Method and device for contactlessly determining temperature of flow of transport material, and granulating device having such contactlessly temperature-determining device

Abstract

The invention relates to a method and a device for the contactless determination of the temperature of linear and / or granular objects in a transport material flow, for example in a dryer outlet of a pelletizer, in which a radiation field of the transport material flow flowing through a background is detected by means of an infrared sensor system, the temperature of the linear or granular object is determined on the basis of a measurement signal of the infrared sensor system, the temperature of the background through which the transport material flow to be measured flows is varied over time and / or locally by means of the temperature control device, and fluctuations at different background temperatures are determined on the basis of the measurement signal of the infrared sensor system, the temperature of the object is determined on the basis of the value of the measurement signal at the time / location of the minimum fluctuation value, and the position of the minimum fluctuation value is determined on the basis of the values of the measurement signal at the time / location of the minimum fluctuation value.

Description

Technical Field

[0001] The invention relates to a method and a device for contactless determination of the temperature of thread-shaped and / or granular objects of a conveying material flow, wherein the temperature determination is carried out using an infrared sensor in order to determine the temperature of the granules or strands of the conveying material flow. The invention also relates to the use of such a contactless temperature determination device on a granulating device, in particular at the outlet of a granulator dryer or a strand granulator of a granulating device. Background Art

[0002] For the processing of pellets and their primary and intermediate products, accurate temperature determination is both important and difficult. Since too high or too low a temperature of the strands or pellets to be processed can lead to process problems, an accurate temperature determination is required, wherein the respective temperature needs to be known as accurately as possible at different points in order to be able to control the process in a targeted manner. In the various upstream process stages, various control variables such as melt temperature, water temperature, water flow rate, air flow rate, flow rate of cooling water nozzles, surface area-volume ratio of the pellets or strands, residence time, etc. can be adjusted in order to change the object temperature at the measuring point in a targeted manner. Many of these control variables have a linearizable correlation with the object temperature at the operating point, and it can be taken into account that such a change can only take effect at the measuring point after a certain delay time. For temperature control, control variables and response times are not a problem. Sometimes it is not necessary to control to the target temperature at all, but to maintain a temperature window, because other important process variables must also be controlled. However, the difficulty so far has been that without reliable, accurate temperature measurements, it is impossible to control the temperature to the temperature window, which is exactly what the present invention is intended to change.

[0003] A granulation process can be used for the production of plastic granules, wherein a plastic melt is usually extruded through a nozzle-shaped hole to produce plastic strands. According to the granulation technology, as known in underwater granulation or dry granulation, the strands produced can be cut directly at the outlet of a perforated plate by a knife rotating there, wherein in underwater granulation the pellets or granules are dried in a downstream dryer. Alternatively, in strand granulation, the plastic strands can first be passed in a linear form through a cooling section and then fed into a strand granulator, where the strands are subsequently cut into granules between a fixed knife bar and a rotating cutting rotor. However, this granulation process is not only used for plastics or plastic melts, but can also be used in the pharmaceutical industry to produce tablets or pills, or in the food industry. In order to obtain high-quality products, precise temperature control of the processed material is required.

[0004] If, for example, the temperature or the cross-sectional temperature distribution in the strand that is still to be pelletized is incorrect, the cutting quality may be affected, so it may also be necessary to accurately determine the temperature of the plastic strand or material strand at different locations between the nozzle plate and the strand pelletizer. By measuring the longitudinal temperature gradient or the temperature measurement values ​​of two or more evaluation sections along the flow direction of the conveyed material, conclusions can be drawn about the core condition of the strand, which should not be a hot, low-viscosity molten state for cutting. On the other hand, process problems can also occur after shredding if the temperature of the pellets deviates too much from the specified temperature window. For example, plastic pellets or granules that are capable of crystallization require a specific temperature that is on the one hand high enough to be able to initiate an energy-saving self-crystallization process using their own heat, but on the other hand not too high to avoid the plastic pellets sticking together. In particular, the pellets should have a predetermined temperature at the outlet of the pellet dryer before they are fed to the corresponding post-processing section or post-processing station (e.g., a vibrating conveyor or a reaction vessel).

[0005] However, for various reasons, the temperature determination of such strands and granules is difficult and has hitherto only been sufficiently accurate. On the one hand, this is due to the fundamental problem that the temperature measurement is to be carried out on a moving object. When the temperature is to be measured, the plastic strands or granules are moving, whereby, for example, at the outlet of a centrifugal dryer, there is no slow, dense stream of granules flowing past, but rather granules that are swept up by the air flow and fly more or less past. Depending on the material, the granules should remain fluidized during the temperature measurement, otherwise agglomerates may form. This applies in particular to plastic granules made of plastics that tend to stick together, but this can also be the case with pharmaceutical or food-grade granules.

[0006] On the other hand, the strands and pellets whose temperature is to be measured are usually very small, so that the sensor system used needs to have sensitive and highly dynamic response characteristics in order to respond adequately to the correspondingly small amounts of heat or radiation emitted by the small objects, especially in view of the sometimes very high speeds at which the pellets flow through the sensor system or the rapid lateral vibrations of the strands (vibrations excited by the pelletizing process). Depending on the material, the diameter of the strands and pellets is usually only a few millimeters or even a fraction of a millimeter, for example less than 7 mm, often less than 4 mm, and therefore very small compared to the dimensions of the detection range of the infrared sensor.

[0007] In this regard, contact temperature sensors have been used to date, which are arranged in the product flow together with thermocouples. However, the problem is that only a small amount of heat is transferred from the product flow or the objects flowing through to the thermal sensor. When the object is in contact with the thermal sensor, the Hertzian contact area is very small, the contact time is very short, and the thermal conductivity of the material (usually plastic) is very low. Instead, the surface of the thermal sensor continuously radiates heat to the environment, while absorbing the thermal radiation of the environment and exchanging it with the air by convection. If a typical pellet dryer with a vacuum blower is considered, the outflowing pellets flow out of the outlet together with a moist and hot air boundary layer. Countercurrently to this flow, dry and cold ambient air is sucked in, which flows into the dryer at the outlet countercurrently to the pellet flow. The ratio of the cooler counterflow to the vortex airflow of the warm air carried by the pellets depends on many parameters and can hardly be adjusted in a reproducible manner. Therefore, the result of a contact temperature measurement is usually only a measurement result obtained by combining the air temperature of the various air flows, the product temperature and the pipe temperature of the outlet pipe.

[0008] In addition, attempts have been made to carry out contactless temperature measurement, where, for example, infrared sensors can be used for plastic granules in the range of 20°C to 150°C, which evaluate the radiation emission of the granules or strands in the wavelength range of about 8 to 14 μm, where pyrometers and radiometric infrared cameras can be used. The response delay of the fastest commercially available sensors is Slightly less than 10 ms, this results in particles or granules flowing through the measuring point of the infrared sensor generating a measuring signal that can be identified as a peak, but the residence time at the measuring point is far from sufficient for the individual pixels of the pyrometer or the radiometric infrared camera to be controlled to the complete particle or granule temperature. The situation is similar for vibrating strands, which can only be partially detected by the pyrometer or pixel due to their small width. The maximum temperature of the individual peaks is significantly lower than the actual object temperature measured by temporary accumulation or aggregation. This is unacceptable and hardly usable. As mentioned above, in the case of strands and plastic granules in particular, such compression of the product flow is not permitted due to the risk of agglomeration and can only be carried out under laboratory conditions or for test purposes, but not in a continuous process in a large plant.

[0009] Direct infrared measurement is only possible when the product filling level is high and a compact sliding layer is formed in the outlet pipe or channel, but this is undesirable or even impossible for many products. Similar problems arise when measuring strand temperature, where very high resolutions of very expensive infrared cameras are required due to the thin strands, or multiple cameras must be installed on the scanning beam at high cost.

[0010] Even with high-performance infrared sensors in the form of pyrometers and bolometers, which have only moderate resolution, strong signal noise can still occur, where the longer response time prevents the sensor from fully adapting to the particle temperature. It can be said that the particles fly past the sensor or pass through its measuring point too fast for the sensor to respond adequately. Both situations ultimately stem from Boltzmann's law, according to which the radiant power reaching the sensor depends on the area and temperature of the particle and on the measuring distance, more precisely P Sensor＝ ε×σ×A×T 4 / r 2 , where ε is the emissivity of the plastic, σ is the Stefan-Boltzmann constant, A is the area of ​​the pellet, T is the pellet temperature, and r is the distance between the sensor and the pellet. For infrared sensors, the pellet temperature is already very low in the range of about 40°C to 120°C, and the radiating surface of the pellet or strand is also very small. In addition, the distance to the sensor is usually very large compared to the pellet size. Therefore, 1 / r 2 The distance dependency results in a very weak measurement signal. For infrared cameras with lower resolution, smaller particle and wire sizes lead to problems, so that the pixels only partially receive the radiation from the object. Only when the pixels are continuously fully covered, the actual particle or wire temperature is gradually approached and the signal noise decreases, provided that the particle or wire is in the vicinity of the sensor for a long enough time, which is not the case in large-scale processes with high production rates.

[0011] Document DE102016115348A1 attempts to achieve non-contact temperature measurement of glass fiber strands using a thermal imaging sensor, wherein the problem of the movement of very thin strands relative to the significantly larger pixels of the thermal sensor and the problem of only a small temperature difference between the strand and the background are compensated by integrating the measurement signal of the thermal sensor over a longer period of time and comparing the formed integral with a reference quantity, which can be determined by a correspondingly long background measurement without fiber passing. In this case, a black body radiator is used as a background radiator, whose reflectivity should be at least approximately 0 to avoid reflection of thermal radiation in the thermal image of the sensor. By forming the integral, it can be said that an average value is determined, which should be more accurate than the maximum value of the measurement signal of the thermal sensor at a certain point in time. However, in practical applications in large plants, it is almost impossible to place a black body radiator near the strand for a long time due to contamination problems. On the other hand, if the actual temperature of the measurement background changes compared to the reference measurement value due to fluctuations in process control, this necessary reference measurement inevitably leads to more or less inaccuracies, which often occurs in large-scale processes.

[0012] Document WO2014 / 090994A2 attempts to measure the temperature of a metal strand covered by an insulating plastic sheath in a non-contact manner using a radiation sensor that performs spatially resolved thermal radiation measurements on the inside of a pipe through which the metal strand passes, wherein the pipe should also be designed as a black cavity radiator so that, given a sufficiently long pipe length, edge losses can be minimized so that measurements under gloss inclusion conditions (Glanzeinschlusses) can be performed in the center. The document is based on the following finding: When the temperature of the metal strand and the cavity radiator is the same, the metal strand can no longer be seen against the background formed by the inner wall of the pipe, so that in the spatially resolved thermal sensor image, no significant deviations occur in the area of ​​the moving metal strand. On the one hand, using this knowledge, the temperature deviation between the metal strand and the known pipe temperature can be inferred from the deviation between the radiation sensor signal and the reference measurement at a known pipe temperature. On the other hand, the above knowledge is used to control the temperature in the following way: the tubular cavity radiator (whose temperature is easy to measure) is temperature-controlled to the desired target temperature, and then the process parameters affecting the temperature of the metal strand are adjusted again when the measurement signal of the thermal sensor exceeds or falls below the corresponding target value, which target value exists at the temperature of the metal strand corresponding to the pipe temperature. In this way, the temperature of the strand can be adjusted to the target temperature, but if the temperature of the strand does not reach the target temperature, the temperature of the strand cannot be measured. Only non-calibrated measurement values ​​with deviations from the background temperature are determined, that is, slightly hotter or colder than the background temperature. If the cross-sectional area and the coverage density of the object to be measured are not known, the object temperature cannot be quantitatively calibrated. Temperatures that do not correspond to the target temperature cannot be accurately measured. In particular, it is not possible to monitor whether it remains within the temperature window. Summary of the invention

[0013] On the contrary, the object of the present invention is to provide an improved method and an improved device of the above-mentioned type, which avoid the disadvantages of the prior art and further develop the prior art in an advantageous manner. Preferably, the deviation from the background temperature itself should not only be determined, but also quantified, so that the actual object temperature can be output or displayed in the sense of an absolute temperature value.

[0014] In particular, even with infrared sensors with limited resolution and limited response time, sufficiently accurate non-contact temperature measurements should be possible in conveying streams with small, fast-moving objects (e.g. plastic strands of a strand granulator and plastic granules of a large granulation plant), in particular in plant sections with short structural lengths (e.g. the outlet of a granulator dryer, where objects can move quickly without a large filling degree being required and sufficient fluidization can be maintained). Known infrared measurement solutions under gloss inclusion conditions are generally not suitable for large plants due to the long installation lengths, so special solutions are required here. The temperature measurement results should be suitable for temperature control, in particular for maintaining a temperature window. In order to keep the control technology simple, it is desirable to obtain a low-noise, quasi-continuous measurement signal with a known, stable measurement delay time that is as short as possible.

[0015] According to the invention, this object is achieved by a method according to claim 1, a device according to claim 21 and a granulation device according to claim 34. Preferred embodiments of the invention are subject matter of the dependent claims.

[0016] Therefore, it is proposed to pay attention to signal fluctuations and to study the intensity of the measurement signal fluctuations more closely. The reason for the fluctuations is that the infrared radiation emission is emitted alternately from the object to be measured and the background. In the case of wire materials, especially with the location Intensity fluctuations occur; in the case of particles, these occur in particular over time. Surprisingly, if the granular object is actually present at the measuring point of the sensor for a sufficiently long time, or if the strand is so wide that there is no problem of partial coverage of the sensor pixels, then it is possible to determine what the sensor is measuring from the intensity of the fluctuations in the sensor signal in the case of a simultaneous change in the radiation background. Here, the temperature of the background flowing alongside the conveyed material flow to be measured is varied over time and / or location by a temperature control device, wherein the intensity of the signal fluctuations in the measurement signal generated by the infrared sensor here is evaluated by an evaluation device. In the simplest embodiment, a search can be made for signal fluctuation minima, wherein the infrared measurement signal at these fluctuation minima directly represents the object temperature. At the infrared contrast minimum, the infrared sensor receives equal infrared radiation from the object and the background, as evaluated by its spectral sensitivity characteristics, so that the measurement signal directly reflects the temperature of the object.

[0017] Such measurement signals are often suitable for process control and temperature window monitoring in industrial installations. However, in cases where the background only changes over time, this simple approach can only update the measurement result at a specific point in time and small jumps may occur because the measurement noise makes the position of the fluctuation minimum uncertain. The design of simple control techniques must be relatively conservative and slow. In order to achieve more dynamic control, more complex prediction models must be trained. In order to be able to easily control the process dynamically within the temperature window, a quasi-continuous measurement signal is desired.

[0018] Other challenges lie in achieving accurate temperature measurement with the infrared sensor itself, since the temperature being measured differs only slightly from the temperature of the infrared sensor housing, which means that the sensor element also receives thermal radiation from its own electronics and its own housing. The transmission of conventional infrared optics is also extremely temperature-dependent. Therefore, infrared sensor manufacturers try their best to account for this influence in the measurement signal using self-temperature monitoring sensors and compensation methods with corrective characteristics. This compensation is not perfect, especially when there are temperature gradients in the measuring head, and it deteriorates with aging.

[0019] Therefore, in an advantageous embodiment, measures are taken to improve the accuracy of the infrared sensor, such as sensor head temperature control, methods for reducing emissivity influences without the need for complex two-color pyrometers, additional temperature measurements of the background using an independent measurement method for online temperature compensation of the measurement signal (wherein the temperature compensation value can be updated online in the presence of a conveying material flow or even during production interruptions), and a calibration station with a blackbody radiator (on which the infrared sensor system can be temporarily positioned).

[0020] In addition, various statistical methods are included, which can robustly quantify signal fluctuations on the one hand and filter out the influence of measurement noise on the other hand and provide low-noise temperature values ​​to the regression model using a reference temperature calculated for the measurement background. Using the regression model, the minimum value can be found reliably and with verifiable quality by interpolation or extrapolation, so that reliable and precise object temperatures can be determined quasi-continuously.

[0021] Furthermore, various devices are described which are very suitable for controlling the temperature of the background and the housing so that the object to be measured has a time- and / or location-dependent infrared contrast with respect to the measurement background, so that the object can be measured in a confined space under almost glossy inclusion conditions. If local temperature differences and longitudinal temperature gradients of the object are to be analyzed in the measurement area, the location-dependent background can also be varied over time and / or a plurality of evaluation sections can be defined, wherein the object temperature and the exact measurement position are determined locally for each section using a separate regression model.

[0022] A central starting point for temperature measurement or determination is the analysis of fluctuations in the infrared sensor signal and changes in these fluctuations in relation to the background temperature, wherein the infrared sensor is aligned with the conveyed material flow such that it can also receive infrared radiation from the background, at least temporarily or in certain areas of the measuring field.

[0023] The infrared measurement signal of fluidized, fast-moving granular objects can show highly dynamic temporal fluctuations if an infrared contrast between the measured object and the background is present when evaluating the spectral sensitivity characteristics of the infrared sensor system, since at each moment there is a different object density in the measuring point. On the other hand, the conveying material flow of thread-like objects takes place in the longitudinal direction, wherein the thread can move smoothly or with strong oscillations in the transverse position depending on the position and mechanical guidance. With the infrared contrast of background and thread and infrared sensors in the form of line or area scan cameras, area intensity fluctuations occur especially in the transverse direction of the thread. At one pixel, the background is more present in the image, while at another pixel, the object is more present, which may be smaller than the resolution of the infrared camera, but the relevant sensor pixels are nevertheless controlled in a different manner. In the case of thread vibrations, highly dynamic temporal intensity fluctuations of the measurement signal occur similarly to granular objects.

[0024] If there is no infrared contrast between the measured object and the background when evaluating the spectral sensitivity characteristics of the infrared sensor, the temporal and / or local fluctuations of the measurement signal are minimal, because the infrared sensor can stabilize to the object temperature over a longer period of time. The infrared radiation from the background affects the sensor element with exactly the same intensity as the infrared radiation emitted by the measured object. If the measurement is performed in an environment that can form gloss inclusion conditions and the black body radiator emits uniform infrared radiation from all spatial directions at the object temperature, then it is no longer a problem even if the emissivity of the measured object is not ideally ε=1, but for example ε=0.9. In this case, the object only emits 90% of the infrared radiation. However, the missing 10% is completely compensated by the gloss of neighboring objects or the radiation environment of the same intensity to a total emissivity of 100%, so that the emissivity no longer has any influence on the measurement. In addition, at the infrared contrast minimum, the sensor response time, the pixel partial coverage, the object area density and the movement dynamics of the measured object have practically no influence on the measurement signal, which remains consistent with the object temperature.

[0025] The only difference between the two cases with and without IR contrast is the level of IR contrast, which is measured by the difference between the IR radiation emitted from the background and the IR radiation emitted from the object. If the temperature radiation of the background is higher or lower than that of the object, the measurement signal fluctuates. If the temperature is the same, the radiation is also the same and the fluctuation is minimal. Since the fluctuation is caused by the fact that the IR radiation from the object and the background varies intermittently or area by area, the intensity of the fluctuation is approximately linear with the temperature difference between the object and the background. The greater the temperature difference, the greater the fluctuation; the smaller the temperature difference, the smaller the fluctuation, until the fluctuation reaches a minimum value when the temperature difference disappears.

[0026] For the analysis of these measurement signal fluctuations, it is therefore advantageous to obtain a linear relationship between the fluctuation intensity and the temperature difference in the method for determining the fluctuation intensity amount. In addition, by calculating the fluctuation, the raw data of a large number of measurement signal values ​​can be reduced to a few key data. In order to be able to determine the low-noise fluctuation of the sensor signal with respect to the background temperature, it is advantageous to use a large amount of sensor data and then analyze these sensor data using statistical methods. If a pyrometer is used as an infrared sensor and it, as a single-pixel infrared camera, always only provides a single measured value, then this data is usually recorded in a specific time period (time evaluation partition) and the time fluctuations are evaluated.

[0027] In the case of a line scan infrared camera aligned with a wire or a particle in front of a uniformly temperature controlled background, the fluctuation can be calculated directly from each exposure of an evaluation zone containing, for example, the entire line scan. Most data can be obtained with an area scan infrared camera, especially when the background is temperature controlled to a temperature gradient field. Here, several different location evaluation zones can be defined in order to determine different fluctuations for different background temperatures from a single infrared image. The evaluation can also summarize multiple exposures acquired under similar conditions. Since each evaluation zone now has a location and a time range, the corresponding fluctuation can be determined based on a larger amount of measurement signal data, thus reducing noise.

[0028] The aggregation of data in the evaluation zones is based on the following considerations: For example, a certain amount of measurement signal data is required in order to be able to determine the degree of fluctuation using, for example, statistical methods. All measurement signal data were recorded under similar infrared contrast conditions, in particular at similar background temperatures. Numerous elementary events in the measurement signal (sometimes receiving more radiation from the object, sometimes less radiation) are not relevant for temperature determination purposes and can be explained by a few key data of the evaluation zones:

[0029] - Fluctuation of the infrared measurement signal (e.g., signal amplitude, other various options, see below);

[0030] - a background reference temperature (eg, the background temperature or the reference temperature described below);

[0031] - location (in particular the position of the center of the evaluation zone along the direction of the conveying material flow);

[0032] - time (especially the average between the start and end of the recording);

[0033] - Key data on the frequency distribution of the temperature measurement signal, in particular:

[0034] ○The average value of the temperature measurement signal;

[0035] ○Statistical characteristic value (Statistische Kennwerte);

[0036] o If necessary, other key data at the maximum value in the distribution.

[0037] The design of the location boundaries of the evaluation partitions can be as complex as necessary in order to cover the data points of a narrow background temperature window as accurately as possible. However, if the above eigenvalues ​​are subsequently used as input data for a regression model that does not have the problem of noisy eigenvalues, then there is little point in spending a lot of effort on defining the boundaries of the evaluation partitions. For very inhomogeneously heated backgrounds, a grid of evaluation partitions can be simply defined. In extreme cases, the evaluation partitions can also be considered as single data points. In this case, the fluctuations are the measured signal values ​​themselves, since the regression can also be calculated for this degenerate form of the evaluation partitions. Only in a direct minimum search without regression modeling does a purely temporal variation of the background temperature require that the evaluation partitions contain several data points. Apart from these rather theoretical extreme examples, the use of evaluation partitions is particularly useful for reducing the measured signal data to a few eigenvalues ​​at an early stage.

[0038] In the following, the intensity of the fluctuations can be understood as a measure that is essentially linearly related to the temperature difference between the object and the background. The signal amplitude or the span of the measurement signal is usually suitable as such a measure. In order to have better robustness to abnormal measurements, a small part of the maximum and minimum measurement data can be omitted and the decile range or a differently truncated span range can be used as a measure. The interquartile range is usually less suitable because the data points containing information are excluded as outliers. The standard deviation has proven to be a particularly suitable linear measure of the fluctuations because it is less sensitive to individual outliers than the signal amplitude, takes all data points into account, and is easy to calculate without the need for internal ranking.

[0039] The evaluation subarea is characterized in particular by the background temperature for which the signal data are recorded. The boundaries of the evaluation subarea are selected such that differences in the background temperature are negligible. It is therefore meaningful to determine an average background reference temperature for the evaluation subarea. Since in some embodiments there is no quantifiable determined background temperature, this reference temperature is referred to as reference temperature hereinafter, so that the background temperature can be a reference temperature.

[0040] In order to use the reference temperature as the reference quantity of the regression model, the nonlinear distortion of the background temperature should be avoided so that a simple function can be used for the regression model. Therefore, preferably, the following requirements are put forward for the reference temperature:

[0041] a) The reference temperature should have a substantially linear relationship with the background temperature; in particular, a higher background temperature should result in a higher reference temperature, but with a positive scaling factor between the reference temperature and the background temperature,

[0042] b) For the case of minimum infrared contrast, i.e. the infrared sensor cannot distinguish between the infrared radiation emitted by the object and the background, the reference temperature shall be as close to the value of the real background temperature as possible within technical possibilities, and thus as close to the object temperature as possible.

[0043] Furthermore, it is advantageous if the reference temperature values ​​determined for the time and / or location evaluation zones are as noise-free and stable as possible, the reference temperature being characterized by maintaining a narrow temperature window with respect to the background temperature.

[0044] There are various options for determining the reference temperature specifically in a temporal and / or locational evaluation zone, which differ in particular in terms of sensor technology and the effort required for mathematical modeling. If the evaluation zone covers a specific data acquisition period, it is always assumed that a time averaging or similarity filtering is performed for the determination of the reference temperature, which is not mentioned below. In order to reduce noise or to model the reference temperature using advanced regression models, data from adjacent evaluation zones can also be used if necessary. The background temperature is the surface temperature of the background at which the infrared sensor is aimed.

[0045] For example, the following concepts can be used as reference temperatures, possibly in combination with each other:

[0046] 1) Direct contact measurement of the background temperature, e.g. in the form of a foil temperature sensor glued to the background,

[0047] 2) Indirect non-contact measurement of the background temperature, for example in the form of an additional infrared sensor mounted on the back,

[0048] 3) Infrared measurement signals that fluctuate significantly with time and / or location, but can be filtered by one or more temporally / locally adjacent evaluation partitions before and after the currently processed evaluation partition, as follows:

[0049] a) Averaging or appropriate filtering of the data of one or more partitions, which in particular averages out short-term and local fluctuations but causes the reference temperature to vary by a factor of (1-A) obj / A tot ) is reduced, and therefore, in particular, the relative object area density A in the conveying material flow obj / A tot In the case of higher temperatures, the temperature change is smaller than that of the background.

[0050] b) If data points of the measurement signal of one or more partitions are selected using statistical or image processing methods, and these data points are likely to represent a particularly low radiation component from the object surface and a high radiation component from the background, a further statistical method can be used to determine a reference temperature value therefrom, the reference scaling factor of which is closer to 1 than the factor when using averaging as described under a), which is particularly possible in the case of a harness running quietly in front of a background.

[0051] 4) Indirect background temperature measurement with back contact, for example in the form of a resistance thermocouple or thermocouple. During the heating and cooling cycles of the temperature control device, due to the non-ideal heat conduction in the wall thickness of the background, a certain temperature gradient will be generated, which is the reason why the background temperature lags behind the externally measured temperature, resulting in systematic measurement errors. Various methods can be used to minimize this error, which is especially important for time-varying measurement backgrounds:

[0052] a) simulating the heat flow through the background wall and estimating the reference and background temperatures based on an assumed heat flow model and an assumed or optimized thermal diffusivity in the wall,

[0053] b) additionally measuring the heat flow of the temperature control device on the back side of the background using a heat flow sensor and simulating the reference temperature and the background temperature based on a measured heat flow model and an assumed or optimized thermal diffusivity in the wall,

[0054] c) make the heating and cooling cycles symmetrical so that they have comparable temperature change rates as they pass through the minimum IR contrast, where the FIFO data buffer always contains the same number of heating cycles and cooling cycles with the same fluctuation minimum, so the regression model automatically compensates for the fact that the reference temperature is sometimes slightly higher and sometimes slightly lower,

[0055] 5) In addition, the redundancy of the reference temperature can be determined using the measurement data of contact or non-contact temperature sensors as well as the non-contact measurement data of the infrared sensor system to achieve higher accuracy, better stability, mutual monitoring of sensors, collaborative calibration and analysis of material flow density.

[0056] In particular, the reference temperature can be determined:

[0057] a) as the weighted arithmetic mean of Concept 3 and Concept 4,

[0058] b) Optimizing the parameters of the thermally guided simulation model 4a or 4b by using the measured data according to concept 3 to minimize the time / location offset. Thus, the reference temperature determined according to concept 3 differs from the reference temperature determined using the optimization concept 4a or 4b by only a proportionality factor. The weighted arithmetic mean of concept 2 and the optimization concept 4a or 4b can be used as the reference temperature for the regression. This includes the option of using only concept 3 or only one of the optimization concepts 4a or 4b.

[0059] Variant 5b is particularly advantageous because, after the two independent reference temperature methods have been matched to each other, the same reference temperature should be determined independently of each other at the contrast minimum. In particular, after the model adaptation of concept 4a or 4b has been performed, the temperature compensation value T can be determined at fixed intervals using the more reliable temperature measurement. c (temperature compensation) in order to adjust the measuring signal of the infrared sensor to a more reliably determined reference temperature, see Figure 3 and its description.

[0060] In order to precisely locate the fluctuation minimum, function models are particularly suitable, which can be determined by approximation from a point cloud of noisy fluctuation data, for example by regression calculations and least squares methods and models based on machine learning. For such function models, the minimum can be calculated directly using mathematical methods. Advantageously, the background of the measured object varies with time and / or location, which is why it is reasonable to establish a regression model, for example, by plotting the fluctuation amplitude with time or location. This is possible, but has the following disadvantage: the desired result (i.e. the object temperature) cannot be determined directly from the regression, but can be read from the measurement signal at the time / location of the determined minimum in a second step. Since it is known that the measurement signal is noisy, it is usually helpful to apply suitable data filtering methods, in which the recorded data of the measurement signal near the time or location of the found fluctuation minimum can be used for filtering, for example by averaging. In addition, the fluctuation minimum must be contained in the recorded data, because simple extrapolation is not possible. Another disadvantage of direct regression with respect to time or location is that the functional relationship between the measured signal fluctuations and time or location may be distorted by nonlinearities of the temperature variation over time or location, so that more complex and therefore potentially less stable modeling helps to achieve a good function approximation. It is also possible to select which data are suitable for the function approximation used for the minimum search. Simple direct regression models for the signal fluctuations in time or location can be calculated, in particular when the temporal variation of the background is realized by a temperature ramp with a time-constant rate of change or a location variation with a uniform temperature gradient field.

[0061] Advantageously, a reference temperature (e.g. background temperature) is selected for the regression modeling of the fluctuation. The fluctuation (e.g. fluctuation amplitude) is substantially linearly related to the infrared contrast of the object temperature relative to the background temperature. The regression model with the reference temperature defined above as the reference quantity enables the position of the fluctuation minimum determined according to the function to correspond directly to the measured object temperature. Now, each data point in the point cloud used for the regression calculation has two scatter points: the uncertainty of the determination of the fluctuation in the ordinate direction and the uncertainty of the determination of the reference temperature in the abscissa direction. The more data is available, the more accurately the minimum can be determined. At a stable object temperature, the redundantly collected data points are close to each other. Thus, when the background temperature changes over time, multiple heating / cooling cycles can be represented in the point cloud, but at the expense of longer delay times. When the background temperature rises from a temperature below the object temperature and approaches the object temperature, the fluctuation amplitude decreases with the increase of the background temperature. The fluctuation minimum is reached at the infrared contrast minimum when the object and background temperatures are equal, and the fluctuation amplitude increases again as the background temperature continues to rise. This applies to the time course in the heating cycle as well as the location course against the temperature gradient. The fluctuations plotted against the reference temperature form a cloud of points with minimum values. In the left region of the colder background temperature, the fluctuation intensity decreases with increasing background temperature, and in the right region it increases.

[0062] If, for various reasons, the background temperature does not change to the extent that the fluctuation intensity reaches and passes through the minimum, the background temperature at which the fluctuation minimum occurs can still be determined by extrapolation. The point cloud of the fluctuation intensity at the reference temperature no longer contains the minimum. Nevertheless, a regression analysis can be performed. The object temperature at which the fluctuation intensity extrapolated from the functional relationship reaches zero or a predeterminable value is output as the background temperature.

[0063] For processes that require measuring sudden changes in the temperature of an object in a highly dynamic manner, an area scan infrared camera with a gradient background should be used. Since a single image contains the entire point cloud of the regression model, this scenario allows for instant measurement evaluation for each exposure.

[0064] If a local change in the object temperature in the measuring area is to be determined and this change can be particularly relevant along the flow direction of the conveyed material, a plurality of sections can be provided, in each of which the object temperature and the exact measuring position are determined. Fig. 9 A method is described in which the change in temperature over time and location can be used to determine the longitudinal temperature gradient.

[0065] For many infrared temperature measurement methods, the emissivity (material property of the measured object) must be compensated by multiplicative emissivity correction or expensive two-color infrared measurement techniques. Although the emissivity of plastics is usually as high as 85-95%, it still has to be compensated for in order to achieve accurate measurements. A lot of laboratory work is required to determine the emissivity of each solution and transfer it to the system. An ideal black body radiator has an emissivity of 100% and a reflectivity of 0%. The radiator temperature can be calculated directly from the infrared radiation emission using Boltzmann's law. For example, a plastic object with an emissivity of 90% reflects 10% of the radiation on the surface as gloss. Linear or granular objects conveying a material flow are usually convex, so that the infrared sensor receives reflected thermal radiation from very different directions on the surface of individual parts of the measured object. At the edges of objects, there is sometimes a gloss angle configuration (Glanzwinkel-Konstellation), which reflects radiation emitted by neighboring objects of almost the same temperature. This self-illumination with the effect of increasing the emissivity can still be compensated in regularly arranged wires, but in chaotically fluidized granular flows, the self-illumination situation cannot be controlled.

[0066] From the measurement setup for gloss inclusions, it is known that the influence of the emissivity can be almost eliminated. To this end, the surroundings of the measuring point can be heated to a temperature by means of a housing thermostat, so that the infrared radiation corresponds almost to the infrared radiation of a black body radiator at the temperature of the object. Ideally, there would be a balanced radiation exchange between the housing thermostat and the object, so that all surfaces emit as much energy as they receive. For wear-resistant surfaces exposed to product wear dust, the housing thermostat cannot be implemented as a black body radiator. Edge effects due to limited installation space and infrared radiation reflected by the housing thermostat should be taken into account. Ideally, the inner surface of the measurement background and the housing thermostat should be uniformly diffuse, non-polarized and have an emissivity of >85%, but preferably at least >70%. If necessary, these properties can be achieved by special coatings. Advantageously, the surrounding surfaces of the temperature-controlled measurement background and / or the temperature-controlled guide body or housing for guiding the conveyed material flow can be provided with a suitable coating, which is preferably made of a plastic or plastic-like material with the above-mentioned high emissivity. Advantageously, a varnish coating and / or a non-stick coating of the guide body surface made of, for example, fluoropolymer and / or silicone may be provided.

[0067] The measurement background is already illuminated with almost correct infrared radiation into the interior of the housing thermostat, minimizing the influence of illumination errors of the housing thermostat that deviate from the object temperature. Radiation edge losses in the entry and exit areas of the housing thermostat are more problematic because the installation length of the housing thermostat is limited in most systems. Radiation losses also occur when the housing thermostat does not seamlessly abut the temperature control background, as is the case with a water bath with a background heating strip across the wire material. All radiation losses together result in the housing thermostat radiating from the inside with a radiation intensity that is slightly lower than the ideal radiation field for measurements with the influence of gloss inclusions. In order to compensate for the non-ideal emissivity of the housing thermostat interior and the radiation losses in the edge areas, the housing thermostat is adjusted to a temperature slightly higher than the measured object temperature.

[0068] In order to reduce edge effects, increase the effective emissivity of the surrounding surfaces of the guide body or the measurement background or bring it closer to 1, and save energy, the measurement background and / or the guide body as well as the housing temperature controller can have thermal insulation properties. Alternatively or additionally, the temperature control device can have a large-area heating and / or cooling element on the surface of the background or the guide body to be temperature controlled, so that the temperature of the surface can be effectively and quickly controlled, thereby achieving a fast cycle to reach the required target temperature. In particular, the planar heating / cooling element located on the surface of the measurement background or the guide body to be temperature controlled for measuring the material flow in the partial area can generate a time and / or regional temperature gradient or a desired regional or time change of the background temperature, during which the fluctuations of the measurement signal are analyzed in the described manner.

[0069] The device for measuring moving objects in front of a temperature-controlled measuring background usually has to be adapted to the conditions of the production plant. The measuring background can be formed, for example, by a tubular or trough-shaped guide body that guides the conveying material flow, but can also be realized as a sliding surface, side, covered surface, freely suspended or surrounded by water or immersed.

[0070] The device for changing the background temperature over time means that, for example, by means of a temperature control device, the background temperature in the measuring range of the infrared sensor can be changed in a heating and cooling cycle, in particular in the vicinity of the object temperature. For this purpose, a pyrometer is the preferred infrared sensor.

[0071] If a line or area scan infrared camera is used as the infrared sensor, a wider measurement area can be analyzed for the background. The temperature of this background can only vary over time and the temperature can be controlled uniformly.

[0072] However, in order to obtain the measurement result more quickly, in particular when using an area scanning infrared camera, it is advantageous if the background has different temperatures, in which case it is suitable to use a background temperature that varies with the location. A temperature variation means, for example, that the background is adjusted to different temperatures by a temperature control device along the distance traveled by the conveying material flow to be measured, or a temperature gradient is established along the conveying material flow path, for example so that the temperature upstream of a guide device for conveying the conveying material in the background is higher than the temperature downstream, or conversely, the temperature of the upstream part of the guide device is lower than the temperature of the downstream part. If the two implementation options are arranged directly in series, two evaluation sections can be realized, and the temperature change of the conveying material flow can be determined by two temperature measurements, so that conclusions can be drawn about cooling measures, the core temperature of an object or an exothermic reaction. In order to be able to detect fluctuations in the sensor signal at different parts of the measuring section, the infrared sensor can also have a plurality of sensor elements distributed in the direction of the material flow, along the measuring section or along the direction of the temperature gradient.

[0073] The temperature gradient in the background can also form any other angle with the material flow, for example perpendicular to the material flow. Non-uniform, circular or periodic temperature fields with temperature gradients in different directions are also possible.

[0074] The aforementioned way of generating a temperature gradient along the conveying flow direction can be achieved by means of heating and / or cooling elements of the temperature control device, which can be distributed along the background. Taking into account the heat conduction occurring in the background material, only a small section of the heating or cooling guide device is sufficient to provide two opposite temperature gradient fields for the two evaluation parts along the flow direction of the measurement area of ​​interest.

[0075] The temperature control device can advantageously include one or more temperature sensors, by means of which the temperature of the measurement background, the guide body or the tubular body can be measured, wherein the temperature sensors can operate in a contact manner. The background temperature between the temperature sensors can be determined by interpolating two adjacent sensor readings at an appropriate distance. Alternatively or additionally, a non-contact sensor can also be provided to determine or calibrate the background temperature field. Depending on the measured background temperature, the temperature control device can be controlled to create a desired location and / or time temperature gradient, which gradient can include in the central part a temperature that is approximately the same as the temperature of the object to be measured.

[0076] Measuring the background can also be achieved by an infrared radiator that emits light through a window material that is sufficiently transparent for infrared radiation. If there are transmission losses, the infrared radiator can be operated at higher temperatures. In the following, the background temperature of such a radiator is defined as the infrared radiation emission evaluated by the sensor in the same way as a normal emission background with an almost ideal emissivity that is precisely temperature-controlled to this background temperature. In order to ensure that the infrared radiator is regarded as an emission background for different temperatures, the radiator can be calibrated with a suitable characteristic curve.

[0077] Devices for changing the background temperature in a targeted manner over time and in a certain area include, for example, a temperature gradient field, wherein the temperature control device changes the average temperature of the entire temperature field in a heating and cooling cycle. Such devices are particularly capable of measuring the longitudinal temperature gradient of an object.

[0078] The control of the temperature control device, in particular the control of the maximum and minimum temperatures in the time and / or zone variation, should be carried out in automatic coordination with the evaluation device. Usually, a certain range around the object temperature is defined as the variation, which range should follow the measured object temperature as symmetrically as possible. By means of the above-mentioned temperature control device, the average target temperature of the measurement background can be advantageously readjusted or adjusted so that objects flowing through in the conveying material flow stand out brightly in the colder background area and produce a clearer fluctuation signal, the fluctuation of the sensor signal in the background area with medium temperature is minimized, and the objects stand out in front of the hotter background area with a darker signal, which again produces stronger fluctuations in the infrared signal.

[0079] In a modification of the invention, a tube can be used as a measurement background and guide body, which can be mounted in a manner that allows rotation about its longitudinal axis and can be rotated about the longitudinal axis manually or by a rotary drive so that the contrast relative to the background can be measured even in the case of a denser conveying material flow, for which the tube can be placed in a transverse rotation position. Similarly, the hole of the infrared sensor can be offset laterally with respect to the central axis, so that the measuring point can be aligned with the nearby tube side. If the infrared sensor has a front mounting flange at an inclined angle to the optical axis, the optical axis can be moved on the conical surface by simply turning the sensor head flange. This makes it possible to align the measuring point with different sub-areas of the conveying material flow, so that a relative object area density in the measuring area in the range of 15-80%, or preferably in the range of 25-70%, can be achieved.

[0080] In an advantageous development of the invention, a temperature control device can be used to keep the infrared sensor measuring head at a nearly constant temperature. Despite fluctuating ambient conditions, the sensor system can still operate within a predetermined narrow temperature window. Higher measurement accuracy, better long-term stability and service life can be achieved at high temperatures and fluctuating ambient temperatures. Advantageously, such a temperature control device for an infrared sensor system can have one or more temperature control elements, for example, on the sensor head of the infrared sensor system. For example, a liquid temperature control unit (for example in the form of a water jacket) can be provided on the sensor head to cool or heat the sensor head and thus keep it within the desired temperature window.

[0081] To calibrate the infrared sensor system, the sensor head can ideally be relocated from the measuring position at the operating temperature to a nearby calibration station with a very ideal black body radiator reference which can be very accurately and uniformly adjusted to the relevant operating point temperature at the measuring point position and can optionally also simulate an infrared scattered light field depending on the measurement situation, thereby calibrating the infrared sensor to the operating point temperature at the relocated calibration position.

[0082] If there is no measured object in the measuring field after the infrared sensor has been repositioned, a transfer calibration to a temperature-controlled measuring background can be performed directly after the above-mentioned absolute working point calibration, wherein ideally the background is stably adjusted to the same working temperature of the blackbody radiator reference, and then a second parallel measurement is performed with the infrared sensor repositioned in the measuring position, wherein the infrared radiation of the background is measured simultaneously and the background temperature is recorded with a contact temperature sensor, so that the emissivity of the temperature-controlled background environment can be determined from the result of the second parallel measurement and saved as calibration parameter for this working point without transferred material flow.

[0083] In order to improve the temperature determination accuracy, the background and environment can be adjusted to the operating point temperature suitable for the next production in the stage without the object to be measured, and the calibration parameters of the operating point without material flow can be used to update the temperature compensation in the aforementioned evaluation module, so that the object can be measured directly with high absolute accuracy at the start of production without manual absolute calibration using a calibration station and a blackbody radiator reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The present invention will be described in more detail below based on preferred embodiments and related drawings.

[0085] Figure 1 A schematic side view of an underwater granulation device with an underwater granulator and a downstream centrifugal dryer is shown, wherein a device for contactless measurement of the temperature of the exiting particle stream is provided at the centrifugal dryer outlet.

[0086] Figure 2A schematic side view of a dry strand granulation device with a water bath is shown with two possible positions of the device for non-contact temperature measurement on the strand and the device for non-contact temperature measurement at the outlet of the sizing screen.

[0087] Figure 3 The outlet in the upper figure and the non-contact temperature measurement device arranged therein are shown in a perspective side view, wherein the infrared sensor system observes the outlet pipe through the cutout in the side of the housing and includes the basic scheme for the data processing of the measurement signals applicable to all subsequent figures.

[0088] Figure 4 Shows something like Figure 3 Stereoscopic side view of an outlet, in which the beam path of the infrared sensor system is folded by a movable deflection mirror, so that a scanning movement following the conveyed material flow can be achieved at the outlet.

[0089] Figure 5 A cross-sectional view showing the outlet with an infrared sensor system attached thereto and means for controlling the background temperature at the measuring point and the temperature of the tubular housing mounted thereon.

[0090] Figure 6 Show Figures 3 to 5 The time course of the measurement signal of an infrared sensor system with a circular measuring point (pyrometer) in FIG. 1 , in particular the time course of the measured background temperature and the fluctuation intensity and the determined object temperature.

[0091] Figure 7 Show Figures 3 to 5 Illustration of an object moving in front of a temperature gradient background measured by an infrared sensor system with an area scan sensor (infrared camera) and the temperature frequency distribution in the evaluation zone.

[0092] Figure 8 Fig. 8A , a perspective view of an infrared sensor system for measuring the temperature of a strand with an area scanning sensor (infrared camera) is shown, wherein a background with, for example, a temperature gradient field is located below the strand and the measuring area is optionally surrounded by a housing thermostat to minimize emissivity effects; Figure 8B A more complex embodiment is shown with the background of two temperature gradient fields for simultaneously determining the temperature of an object in two sections along the direction of the conveying material flow.

[0093] Fig. 9 A diagram showing the local variation fluctuation of the measurement signal of the infrared sensor system in FIG. 8 when using an infrared camera, wherein the background has a temperature gradient field.

[0094] Fig.10A perspective view of an IR sensor system on a wire is shown, where a line scan IR camera or an area scan IR camera is used as the sensor, the IR radiation background is located below the wire, the wire can also be immersed in a water bath, and the measurement area is optionally surrounded by a housing thermostat to minimize emissivity effects. DETAILED DESCRIPTION

[0095] As shown in the figure, non-contact temperature measurement can be used at different locations in large pelletizing plants. The sensor system is suitable for dry-cut or wet-cut pelletizing systems as well as for underwater pelletizing systems. In these and other plants, the sensor system can also be used at various measurement locations other than those shown in the examples.

[0096] Figure 1 A typical extrusion line with an underwater pelletizing device 12 is shown. The melt feeder 15 presses the polymer melt into the cutting chamber 16 of the underwater pelletizer 13 through the nozzle plate 14, in which the discharged strand material is cut into pellets by a rotating knife in water and conveyed to the pellet dryer 17 through a pipeline. The mixture of pellets and water is separated in the pellet dryer. The separated pellets are dried and then discharged from the outlet 18, from which the pellets are usually sent to a subsequent processing station such as a grading screen, a vibrating tank or a thermal container, for example, to carry out a crystallization or self-crystallization process of the pellets.

[0097] The temperature of the granules discharged from the granule dryer 17 at the outlet 18 should be within the process temperature window. If the granules are too cold, the residual heat may not be sufficient to evaporate the residual moisture on the surface. If the granules are too hot, agglomerates may form due to welding. The process temperature window is particularly narrow for polymers, which should maintain a high residual heat in a targeted manner in order to retain sufficient energy to initiate the subsequent crystallization. For some polymers, only a temperature deviation of a few degrees Celsius is allowed, otherwise waste products will be produced. In particular, non-contact temperature measurement can be carried out at the outlet 18 for discharging the dried granules in the form of the conveying material flow 2. The granular objects in the conveying material flow 2 are usually not discharged in the form of a slow-flowing, compact granule stream, but fly through the tubular outlet 18 in a more or less mutually dispersed and fluidized manner. In the boundary layer of the granules, hot and humid air from the granule dryer 17 can also be entrained. In typical operation, an exhaust fan is used to generate a slight negative pressure in the granule dryer 17, so that a dry counter-air flow is sucked into the outlet 18 in the opposite direction to the discharged conveying material flow 2. Overall, therefore, complex flow conditions may prevail in the outlet 18 with different gas flows having different temperatures, which gas flows are guided through the outlet 18 in addition to the granular objects of the conveying material flow 2 .

[0098] An infrared sensor system 1 can be assigned to said outlet 18 and observe the interior of the outlet in order to be able to measure the temperature of the objects 3 flowing through.

[0099] The inner wall of the outlet 18 forms the temperature measurement background 4, wherein in the case of a preferably cylindrical outlet pipe, see Figures 3 to 5 , the inner surface of the tube forms the background 4 for temperature measurement.

[0100] Figure 2 A classic dry-cut pelletizing device is shown, in which a melt feeder 15 extrudes a polymer or other material through a nozzle plate 14 and forms parallel strands 7 which are first directed through a water bath 8 and subsequently cut in a pelletizing device 12. Figure 1 As shown, various subsequent processing stations can be arranged. A grading screen 9 is shown here, from which the conveying material flow 2 is guided to an outlet pipe 18. For temperature measurement on the strand 7, two positions of sensor systems are shown by way of example: a first infrared sensor system 1a is arranged above the water bath 8 (see Fig.10 ), wherein a temperature-controlled background infrared radiator is located in a water bath 8 and the strand 7 still in the water is measured by the infrared sensor system 1a. Preferably, another infrared sensor system 1b with a temperature gradient background is arranged in the inlet region of the granulation device (see Fig. 8A Based on the infrared image of the strands 7 located in front of the temperature gradient background, the individual temperatures of all strands 7 can be measured accurately and highly dynamically, even if the strands fluctuate dynamically here. Figure 8B ), it is possible to check whether short-term strand temperature changes occur between two evaluation sections in the direction of the conveying material flow, for example due to heating of the strand sheath by the hot strand. With the infrared sensor system 1c in the outlet 18, the temperature of the cut particles in the fluidized conveying material flow 2 can be measured (see also Figure 1 and Figure 3-Figure 5 ).

[0101] Various other wet-cut and dry-cut strand granulation devices with automatic strand feeders (not all shown individually here) can also be equipped with non-contact temperature measurement technology for the strands and cut pellets, wherein the sensor system on the strand can be used in particular in the chute area, wherein smaller sections of the chute can be designed as a heated background, or background infrared radiators can be used in the water spray area.

[0102] like Figure 3As shown, the optics of the infrared sensor system 1 can observe the interior of the outlet 18 through the hole 19, so that the infrared sensor system 1 has at least one measuring point 20 inside the outlet 18, and the conveying material flow 2 moves and passes through the measuring point 20. If an infrared camera is used as the infrared sensor system 1, a larger measuring area is detected, wherein each pixel or each pixel group measures a separate measuring point 20. As an example, a granular object 3 moving in the measuring point 20 of the infrared sensor system 1 is shown.

[0103] Advantageously, the inner surface of the outlet 18 and therefore of the background 4 has a high emissivity (Emissionsgrad), which can be achieved by a corresponding design of the outlet wall and / or a suitable coating of the wall surface, which forms the area of ​​the measurement background 4 and the housing thermostat 22. For example, the inner wall side of the outlet 18 can be coated with a plastic-like coating, a varnish, or a non-stick coating made of a fluoropolymer or silicone with a high emissivity.

[0104] The outlet 18 and therefore the background 4 can be temperature-controlled at least in the region of one or more measuring points 20 by a temperature-control device 6 , which can comprise at least one heating and / or cooling element 21 mounted on the wall of the outlet 18 .

[0105] Preferably, a housing temperature controller 22 , for example in the form of a heating sleeve, may be installed near the temperature control device 6 , which at least partially surrounds the outlet 18 and may have a plurality of partitions if necessary to generate different temperatures in different parts of the outlet 18 .

[0106] In particular, the temperature control device 6 can be configured to vary the temperature of the background 4 over the location and / or over time during the measurement of the infrared sensor system 1. The temperature of the entire outlet 18 can also be raised and lowered uniformly by the housing temperature controller 22. If the temperature of the background 4 varies over the location, the temperature control device 6 can heat and / or cool different background subareas 4a-c of the outlet 18 differently, so as to set different temperature fields, for example, along the path of the conveying material flow 2. For this purpose, the temperature field can take any shape, with any number of subareas, temperature minima and maxima, and temperature jumps, as long as different background temperatures occur simultaneously depending on the location. The temperature field can also be varied over time. The background temperature 25 can be measured independently using contact or non-contact temperature measurement techniques, which can optionally be supported by a temperature simulation model, which can combine measurement data from different locations of the background 4, wherein the measurement of the background temperature 25 is not required, but can nevertheless be provided. The conveying material flow 2 usually does not completely cover the background 4, so that a reference temperature 38 can be determined solely based on the measurement signal 29, which is at least partially affected by the background temperature 25. For a non-uniformly temperature-controlled background 4, it is possible, for example, to determine the reference temperature for all zones individually, starting from an arbitrary grid of evaluation zones 45. Then, there is the option of combining evaluation zones 45 with similar reference temperatures 38 into larger evaluation zones 45 and subsequently using these larger evaluation zones 45 and determining their fluctuations 32 and reference temperatures 38.

[0107] The temperature of the background 4 can be controlled by a temperature control device 6 , wherein one or more temperature sensors 23 can measure the temperature of the outlet 18 , and the temperature control device 6 can then be controlled according to the temperature.

[0108] The data processing of the measurement signal 29 takes place in the evaluation device 30. If there are multiple evaluation components 51 (see Figure 8B or Fig. 9 ), then in a first preprocessing step each portion 51 is assigned a corresponding subset of the measurement data.

[0109] In a second preprocessing step, a temperature compensation value T c 40 Correction of the measurement signal 29 .

[0110] Subsequently, a complete individual data processing is performed for each portion 51 , and the measured object temperature 39 is outputted respectively.

[0111] The single data processing process is as follows: on a specific signal data set including a time and / or location evaluation partition 45 with a similar background temperature, the fluctuation intensity of the measurement signal 29 is evaluated by the fluctuation evaluation module 31, and it is output as a fluctuation degree 32 in the form of a fluctuation amplitude, for example, which is substantially proportional to the infrared contrast measured between the object and the background. Other determination methods of the fluctuation degree 32 are described in the specification. Other signal data sets of other evaluation partitions 45 are evaluated in the same way, so different fluctuation degrees 32 are obtained for different background temperatures 25. If the background temperature 25 changes with time, it takes a certain amount of time to detect different evaluation partitions 45; if the background temperature 25 changes with location, different evaluation partitions 45 can be detected and evaluated at the same time. For each time and / or location evaluation partition 45, a reference temperature 38 is determined in a reference temperature determination module 37, and the reference temperature 38 can be used as a reference quantity for the regression model 33. The reference temperature 38 can be calculated based on, for example, the average background temperature 36 or the average infrared measurement signal 35, their weighted arithmetic mean, and various other methods. This specification describes in particular a method for internally determining two reference temperatures by means of two independent calculation paths using image processing, statistics and heat diffusion modeling: modeling a - based on infrared measurement data 29, and modeling b - based on background temperature 25 and heat flow measurements 54 of an optional heat flow sensor 53. Based on the difference Δ between modelings a and b, the temperature difference T can be determined with a fixed period for the minimum of fluctuations. c 40 , for carrying out said temperature compensation of the measurement signal 29 in a preprocessing step of the evaluation device 30 .

[0112] In the regression module 33, the functional relationship between the fluctuation 32 and the reference temperature 38 is determined and the measured object temperature 39 is determined by a minimum search 34 or, in the case of extrapolation, the intersection of the regression function with the zero axis or a predetermined value is determined.

[0113] If the background 4 is divided into a plurality of evaluation sections 51 which may be as small as a line of pixels (see Figure 8B and Fig. 9 ), the object temperature 39 can be determined for each part using a part-specific regression model 33 for the area of ​​each part. If the background temperature field has, for example, a complex temperature gradient 48 (see, for example Figure 8B ), so that the infrared contrast minima of the object 3 relative to the background 4 appear in two or more evaluation sections along the conveying material flow path, a certain spatial resolution in the direction of the conveying material flow 2 can be achieved by determining the local object temperature 39 in the differently located sections 51. The more sections 51 are provided in the case of a suitably temperature-controlled background 4, the finer the spatial resolution.

[0114] In the evaluation section, for example, the upstream section 4a of the outlet 18 can be cooler than the conveying material flow 2. The middle section 4b of the outlet 18 can be temperature-controlled at least approximately to the temperature of the conveying material flow 2. The downstream section 4c of the outlet 18 can be made to have a higher temperature than the conveying material flow 2 (see Figure 7 ).

[0115] Figure 4 It shows that Figure 3 The fixed measuring point shown is compared to the periodically deflected measuring point. The beam path of the infrared sensor system 1 is folded at a dynamically changing angle, for example by rotating the prismatic reflector 24. The measuring point 20 or the measuring area of ​​the infrared camera is moved due to the deflection so that it follows the flow direction of the conveyed material flow 2 at a speed that is as similar as possible to the moving object 3. For this purpose, a hole 19 is processed in the outlet 18 in the shape of an elongated slit in the direction of movement. The temperature control device 6 or its heating and / or cooling element 21 is also designed to be elongated accordingly (the same is true for the housing temperature control 22) so that a longer outlet section or background section can be temperature controlled.

[0116] In the case of a prismatic reflector 24 with a continuous rotation speed, the angular relationship or the varying distance does not result in a completely constant scanning speed of the measuring point 20. However, the rotation speed of the prismatic reflector 24 can be controlled in accordance with the angle so that the measuring point 20 moves along the background 4 in front of the background 4 at a practically constant speed. If the scanning speed of the measuring point 20 is well matched to the speed of the conveying material flow 2, the time for which the infrared sensor system is stably aligned with the moving object 3 will be significantly increased. As a result, the temperature of an individual moving object 3 can be measured and the temperature distribution of the objects in the conveying material flow 2 can be determined. The temperature control device 6 is advantageously composed of a plurality of individually controlled heating / cooling elements 21 in order to form a temperature gradient field of the background 4, in particular a temperature gradient field of the background 4 transversely to or along the scanning direction. The background temperature at the position where the contrast of the moving object 3 disappears represents the temperature of the individual object.

[0117] like Figure 5As shown, the infrared sensor system 1 can also observe the interior of the outlet 18 at an angle. When the measuring point 20 is fixed, this inclined arrangement at an angle of, for example, 30° to 80° or 35° to 55° to the longitudinal axis of the outlet can be set, but in principle this inclined arrangement can also be set when using the above-mentioned prismatic reflector 24. Here, the housing temperature controller 22 is designed in the form of a heating sleeve, which has a recess for the temperature control device 6. A water temperature control sleeve 5 is arranged around the measuring head of the infrared sensor system 1, which enables the sensitive sensor system to operate in a temperature-stable state. Advantageously, the infrared sensor system 1 can operate within a narrow temperature window by active temperature control, so that even if the ambient conditions fluctuate, the sensor system 1 can perform precise measurements with the highest accuracy for a long time, wherein this temperature control can preferably be achieved by the water temperature control sleeve 5 around the sensor head.

[0118] In order to protect the lens of the infrared sensor system 1 from dust or dirt, finely filtered instrument air flows downward from the purge air nozzle 27 to the conveying material flow 2. In the heat transfer contact from the temperature control device 6 to the outlet 18, a combined temperature and heat flow sensor 53 can be optionally used. Thereby, the heat flow transferred to the outlet 18 can be measured during the heating and cooling operation of the temperature control device 6, and as described in the description, the temperature of the background 4 can be determined more accurately based on the known thermal conductivity of the wall material.

[0119] like Figure 6 As shown, the background temperature 25 of the background 4 varies with time, which can be determined, for example, by Figures 3 to 5 One of or Fig.10 The infrared measurement signal 29 (shown here in simplified form as thin wavy lines) fluctuates very dynamically, because at the measuring point 20 of the infrared sensor system 1 sometimes more infrared radiation is received from the object 3 and sometimes more infrared radiation is received from the background 4. The greater the fluctuation amplitude 32a of the measurement signal 29, the greater the deviation of the background temperature 25 from the object temperature 26. The measurement signal 29 actually always fluctuates only between the object temperature 26 and the background temperature 25, so that this fluctuation almost disappears when the object temperature 26 and the background temperature 25 are the same, that is, when the radiation of the object cannot be distinguished from the radiation of the background 4 in the spectral evaluation of the infrared sensor system 1. In the case of such a contrast minimum 42, the value of the determined object temperature 39 can be obtained directly from the measurement signal 29, for example from the measurement signal 35 averaged by a low-pass filter, or from the background temperature 25.

[0120] In order to regularly achieve such a contrast minimum 42, the background temperature 25 can be increased and lowered again, in particular periodically, wherein the average value between the temperature increase and decrease can also be changed at the same time, in order in particular to bring the average background temperature 25 approximately close to the object temperature 26. Figure 6 As shown, the temperature cycle is initially too low, that is, the temperature rise cycle Still below the object temperature 26. However, if the average temperature is also adjusted, the background temperature 25 and its variation can be set so that the background temperature 25 oscillates around the object temperature 26 (see Figure 6 right half of the ).

[0121] In particular, the degree of temperature variation of the background 4 is selected here so that when the background temperature 25 changes, these fluctuations 32 also change, so that the fluctuations 32 periodically reach a minimum when the infrared contrast between the object and the background disappears. The fluctuations 32 are plotted on Figure 6 On the right vertical axis, where “∝SD[T IR ]" means that it is proportional to the standard deviation of the infrared measurement signal. If the background temperature 25 rises above the object temperature 26, the fluctuation 32 will increase. If the increase in the background temperature 25 decreases again, the fluctuation 32 will decrease again until it passes through the fluctuation minimum again. If the background temperature 25 then drops below the object temperature 26, the fluctuation 32 increases again; and when the background temperature 25 rises again from the reduced state, the fluctuation 32 decreases again, so that when the background temperature 25 reaches approximately the object temperature 26 again, it passes through the amplitude minimum again.

[0122] Through Figure 3 The evaluation device 30 shown evaluates the measurement signal 29 of the infrared sensor system 1. In the time-limited evaluation partitions 45 (the time of the evaluation partitions 45 is very short, so that it can still be assumed that the background temperature 25 is essentially unchanged), the fluctuation 32 is calculated for each evaluation partition 45. The acquisition period for recording the measurement signal 29 in order to be able to determine the fluctuation 32 of the evaluation partition 45 can be defined within wide boundaries until it only consists of a single data point, and the actual fluctuation analysis is carried out in the subsequent regression calculation. However, in many cases, it is advantageous to reduce the large amount of measurement signal data 29 to a few characteristic values ​​at an early stage and summarize the data, for example, in the range of a few tenths of a second to a few seconds. The instructions give various calculation options for calculating the fluctuation 32. The individual measured values ​​of the measurement signal 29 are recorded in a short cycle in order to determine the fluctuation 32 of the measurement signal 29.

[0123] At the same time, the measured values ​​of the background temperature 25 are averaged within the same cycle. In this example, the time-synchronized data of the fluctuation 32 and the associated average background temperature 25 are temporarily stored as reference temperature 38, for example in a FIFO data buffer, for use in the regression evaluation.

[0124] If measurement data of the background 4 can be obtained from one or more temperature sensors 23 in a manner independent of the infrared sensor system 1, the contrast minimum 42 provides a good opportunity to cooperatively calibrate the measurement signal 29, which may be influenced by many interfering variables, based on, for example, the background temperature 25 determined more reliably by these same temperature sensors 23. In addition, in phases in which the object temperature 26 is apparently constant over a longer period of time, the background temperature 25 can be controlled to be as close as possible to the object temperature 26 for a certain period of time. In this stable state of the contrast minimum, there is sufficient time for the signal of the temperature sensor 23 to match the background temperature 25, and in particular when, after the stabilization phase, it has been verified by the temperature change of the background temperature that the object temperature 39 that can be determined before and after is almost the same, the difference between the infrared measurement signal 29 and the background temperature 25 measured by the temperature sensor 23 can be used directly as the temperature compensation value 40.

[0125] Figure 7 shows that it can be used according to Figures 3 to 5 Evaluation of a measurement signal image or a portion thereof (as an image portion of a multi-part measurement signal image of an infrared sensor system 1 in the form of an area infrared camera) by a device. Figure 7 A moving object 3 in a conveying material flow 2 flowing in the X direction 41 in front of a background 4 with a uniform temperature gradient field 48 is shown in a false color temperature visualization. The background 4 is colder than the object 3 in the upstream part 4a, has almost the object temperature 26 in the middle part 4b and is hotter than the object 3 in the downstream part 4c. The temperature field of the background 4 can also have different and other gradient directions and quite complex non-uniform temperature fields with different temperature areas and jumps, which creates the prerequisite for measuring the moving object 3 at different locations in contrast to different background temperatures 25. The evaluation zone 45 containing a specific background temperature window can be realized in a simple form in the uniform temperature gradient field by a rectangle roughly delimited by isotherms 44. For non-uniform background temperature fields, more complex geometric shapes or grids can be used for the location boundaries of the evaluation zone 45, for example, see the description.

[0126] Since the dwell time of the object 3 in the measuring point 20 of the pixel 47 is short relative to the response time of the infrared sensor system 1, the measurement signal 29 of the excited pixel 47 reacts in a time-delayed manner, resulting in an afterglow track with soft edge transitions, which is shown here in a simplified manner as a high-contrast ellipse 3. Figure 4 In the case of the arrangement shown, this afterglow can be minimized so that particles that are precisely matched to the scanning speed of the moving measuring point can be imaged mostly with their real object contour, while individual objects 3 that move slightly slower or faster than the scanning speed only form a brief afterglow track in front of or behind them. This means that the object 3 stays in front of the controlled pixel 47 long enough for the measurement signal 29 to achieve complete amplitude adjustment, from which the individual object temperature 39 can be determined for each individually detected object 3 by simple image processing.

[0127] In order to determine the average object temperature 39, the various fluctuations 32 are determined from the infrared image of the measurement section in different evaluation zones 45, which in the example shown are formed by temperature windows of + / -0.15° C. around the corresponding average background temperature 25, which are bounded by isotherms 44. Figure 7 The nine evaluation zones 45 are evaluated in . For this purpose, the measurement signals 29 of all pixels 47 within the respective evaluation zone 45 are statistically evaluated, wherein the standard deviation is particularly suitable for determining the fluctuation 32. In the description, alternative statistical characteristic values ​​such as the span range or the interdecile interval are discussed. In order to intuitively display the statistical dispersion of the measurement signal 29 within the rectangular evaluation zone 45, Figure 7 The lower edge of shows a temperature histogram 43, which is associated with the data in the corresponding evaluation partitions 45 in the upper infrared image, wherein only the evaluation partitions 45 associated with the reference histogram 43b are explicitly shown. For each evaluation partition 45, a reference temperature 38 is determined, which can be achieved, for example, by averaging the background temperature 25 of the area or by other methods described.

[0128] In the pseudo-color image, for each pixel column, the local infrared contrast relative to the central axis of each evaluation partition is given by the relative temperature T rel 46, the black dashed line indicates that T relis calculated as the difference between the measurement signal 29 and the reference temperature 38 of the corresponding evaluation zone 45. The infrared contrast is embodied in the temperature histogram 43 as the distance between the maximum values ​​49 and 50 of the temperature distribution. All histograms 43a-i have the same temperature axis scale, wherein in each case only the reference temperature 38 is marked. The distance between the maximum values ​​49 and 50 is particularly large in the downstream part 4c in the histogram 43i and in the upstream part 4a. In the middle part 4b, the temperature histogram 43e shows only the central maximum value, because the object 3 has an object temperature 26, which is almost the same as the background temperature 25, so that there is no infrared contrast. In this middle part 4b, the pixel 47 of the infrared sensor system 1 remains almost stable when the measurement point 20 associated with it is in a state of balanced radiation exchange (ausbalancierten Strahlungsaustausch), so as an alternative to the regression method, it is also possible to read the temperature value at the position of the main maximum value 49 in the histogram 43e with the smallest standard deviation as the measured object temperature 39, which is 81°C in this example. A disadvantage of this method is that during the successive measurements at different locations of the object 3 , the determined object temperature 39 can jump between the measurements of different evaluation zones 45 .

[0129] For the evaluation method, the angular orientation of the conveying material flow 2 relative to the background temperature gradient field 48 is not important, as long as it can be assumed that the object temperature 26 remains approximately constant at all locations in the infrared image or in a part of the infrared image. In the case of a non-negligible cooling of the object temperature 26 during movement over various regions of the background 4, it may be advantageous to orient the temperature gradient 48 of the background 4 in the opposite direction to the direction of the conveying material flow 2. This ensures that the object temperature 26, which varies with location, and the temperature of the temperature gradient field 48 clearly intersect and are not parallel in certain areas, which could otherwise cause problems when searching for a minimum 34 in an area of ​​constant fluctuation 32. Orienting the temperature gradient field 48 parallel to the conveying material flow 2 can be useful if the moving object 3 may heat up during the measurement due to an exothermic process, such as a chemical reaction or crystallization.

[0130] If a relevant change of the object temperature 26 in an unknown direction is expected during the movement on the background 4 and it can be assumed that the object temperature 26 is uniform in the transverse direction of the conveying material flow 2, a conveying material flow 2a can be used which flows transversely to the temperature gradient field 48. In almost all cases, it is sufficient to set a sufficiently steeper temperature gradient in the background 4 than the gradient caused by the change of the object temperature 26 during the movement of the object 3 on the background 4.

[0131] Figure 7A special case of the background 4 is also implicitly shown, i.e. it is very narrow and has, for example, only the width and height of one white shaded evaluation partition 45 above the histogram 43b as overall dimensions. As described above, this narrow background 4 can have any temperature gradient field 48, where it should be assumed that the width is narrow to a certain extent so that any temperature gradient present in the X direction can be ignored. For the trend of the background temperature 25 in the Y direction, two relevant scenarios will be discussed in particular:

[0132] Scenario A: The white shaded image area (in this particular case, it includes the entire background 4 of the infrared sensor system 1 or a complete part of the image) has a temperature gradient oriented in the Y direction. The previous description fully covers this case, as it is just a matter of Figure 7 The only difference in the illustration, which is rotated by 90°, is that the conveyed material flow 2 a extends vertically and the afterglow track of the moving object 3 is correspondingly formed in the Y direction.

[0133] Scenario B: The white shaded image area (which in this special case includes the entire background 4 or complete part of the image of the infrared sensor system 1 ) has a uniform temperature in the Y direction.

[0134] The associated histogram 43b visualizes the statistical distribution of the measurement signal 29, from which the fluctuation 32 can be determined, for example using the standard deviation method, which is essentially linear with the infrared contrast. Other statistical methods are discussed in the description. The infrared contrast situation currently visualized in the temperature histogram 43b is as follows: The background 4 (which in this special case is limited to the white-shaded evaluation zone 45) is uniformly temperature-controlled to 78° C. The relative object surface density in the conveying material flow 2 is quite low, so that the maximum value 49 is mainly determined by the pixels 47 that essentially receive infrared radiation from the surface of the background 4.

[0135] Since all pixels 47 are regularly driven by the hotter object 3 to higher measured signal values ​​29 close to the object temperature 26 of 81° C., the main maximum 49 in the temperature histogram 43 b is slightly above 78° C. due to the afterglow effect. Likewise, the secondary maximum 50 does not quite reach the object temperature 26 and is slightly below 81° C. because the pixel 47 does not receive the stronger infrared radiation from the object 3 for a sufficiently long time. This has been explained in detail elsewhere by the fact that the use of the Figure 4This can be achieved better with a device, and the maximum values ​​49 and 50 can thus reach the exact values ​​of the background temperature 25 and the object temperature 26. In summary, the evaluation of the measurement signal data 5 visualized in the temperature histogram 43b in the special case where the size of the background 4 is the same as the white hatched evaluation partition 45 can be explained as follows: the background temperature 25 is still significantly lower than the object temperature 26, and then, for a further increasing higher background temperature 25, at least the initially reduced fluctuation 32 should be recorded in order to determine the object temperature 39 from the time data set of various fluctuations 32 at different background temperatures 25 by regression analysis. This method is similar to Figure 6 The method for varying the background temperature over time and processing the fluctuations 32 in the regression model 33 is identical to that described in . Therefore, for the analysis of the fluctuations of the measurement signal 29, it is irrelevant whether these fluctuations are determined by the temporal variation of a single pixel 47 (i.e. a single measuring point 20 of the infrared sensor system 1 designed as a pyrometer) or by local fluctuations of the infrared intensity (local fluctuations of the infrared intensity are recorded on a narrow background band with a line infrared sensor system 1, which is described in a special case). As an alternative to a line scan infrared camera, an area scan infrared camera can also be used as the infrared sensor system 1, whereby, for example, a method according to Fig.10 As is achieved by the device of , only the pixels 47 of the measurement portion in the form of a strip-shaped image portion (region of interest, ROI) are read out, whose measurement points 20 are aligned with the temperature-controlled strip-shaped background 4.

[0136] Fig. 8A An embodiment of an infrared sensor system 1 in the form of an area scanning infrared camera is shown, which is directed in the field of view at one or more strands 7, which are moved in the longitudinal direction of the strands as a conveying material flow 2. In order to reduce the influence of the emissivity ε of the strands 7 to be measured, it is recommended to use a housing temperature controller 22. In order to reduce edge effects, the hole 19 should not be made larger than necessary. If possible, the emitted light from the strand surface captured from the camera's field of view should come from the spatial direction covered by the housing temperature controller 22, although certain edge effects caused by infrared radiation at ambient temperature 55 can hardly be prevented at the inlet and outlet. Behind the strands 7 is the measurement background 4, which has a slightly structured temperature field with the help of the temperature control device 6, so that different background temperatures 25 appear simultaneously at different locations in the image field of the infrared camera 1. Using a contact or non-contact temperature sensor 23, additional temperature information 25 of the background 4 can be determined, so that based on this temperature information and the information of the infrared sensor system 1, the background temperature 25 of each location of the background 4 can be at least roughly known. However, as for Figure 3As described in the data processing scheme of FIG. 4 , it is sufficient to determine the reference temperature of a temperature region with a similar background temperature 25. In order to be able to measure the strand temperature 26 separately, it is advantageous if the temperature gradient field 48 of the background 4 has a temperature gradient that is oriented substantially in the direction of movement of the strand 7. For example, if a thin layer of water still adheres to the strand 7 and a strong ablation cooling effect is thus generated, the strand temperature 26 will decrease in the direction of the conveying material flow 2. Therefore, in order to obtain a stable regression model 33 for determining the strand temperature, it is recommended to align the temperature gradient field 48 in the background 4 in the opposite direction of the temperature gradient in the strand 7, i.e., hotter than the strand 7 in the downstream portion 4c and cooler than the strand 7 in the upstream portion 4a. In the case of the reverse orientation, the temperature gradient of the temperature gradient field 48 should be sufficiently steeper than the gradient of the strand temperature 26 in the longitudinal direction of the strand.

[0137] To measure the temperature gradient of the strand temperature 26 in the longitudinal direction of the strand, further sections with further background temperature gradients 48 can also be used in the direction of the conveying material flow. The regression model 33 assigned to the respective evaluation section 51 then determines the respective local object temperature 39 of the respective section.

[0138] Figure 8B A simple subdivision of the background 4 into individual sections 51 is shown, wherein the object temperatures 39a, 39b are determined independently of one another for two slightly overlapping evaluation sections 51a and 51b at different positions 41a, 41b of the conveying material flow 2. By means of the temperature control device 6, a lower background temperature 25 is set in the upstream section 4a, a background temperature 25 higher than the strand temperature 26 is set in the middle section 4b, and a lower background temperature 25 is set in the downstream section 4c than in section 4a. In the evaluation section 51a, the temperature gradient field 48a is opposite to the direction of the conveying material flow 2; in the evaluation section 51b, the background adopts a more intensive temperature gradient field 48b in the direction of the conveying material flow. This allows separate evaluations for the evaluation sections 51a and 51b. As an example, a strand 7 is shown in a temperature visualization pseudo-color representation in front of the background, wherein the strand temperature 26 decreases in the direction of the conveying material flow 2. In the evaluation section 51a, a fluctuation minimum is reached in the evaluation sub-area at the position 41a, so that a measured object temperature 39a of about 80°C is reached. In a separate temperature evaluation in a second evaluation section 51b located downstream, a further fluctuation minimum is evaluated at position 41b and a body temperature 39b of approximately 76° C. is determined there. The longitudinal temperature gradient in the strand 7 can now be determined simply as the temperature difference 39a and 39b divided by the distance 52 between the measuring positions 41b and 41a, the exact position values ​​of which are determined for each evaluation section according to the regression.

[0139] Fig. 9 shows how it can be used according to Fig. 8A Method for evaluating a measurement signal image of an infrared sensor system 1 in the form of an area scanning infrared camera of a device. The temperature visualization pseudo-color image can also represent an evaluation portion, i.e. an image portion, so that a plurality of evaluation values ​​can be calculated portion by portion for the entire measurement signal image, see Figure 8B .and Figure 7 The only difference is that here, instead of a moving granular object 3, a continuous strand 7 is running in front of the background 4. The conveying material flow 2 is essentially manifested as a continuous longitudinal movement of the strand 7 in the X direction. Depending on the measurement position and the way the strands 7 are guided, these strands move slightly in the Y direction, but may exhibit dynamic vibrations, especially in the feed area of ​​the granulator. In production plants, it is often necessary to measure dozens of parallel strands 7. The background 4 has a temperature similar to the object temperature 26 and has different temperatures 25 in the area, specifically a temperature gradient field 48, which allows the infrared sensor system 1 to be placed relatively far away so that the measurement resolution of the infrared camera 1 can just distinguish the strand 7. For fluctuation evaluation, even if vibrations occur in the strand 7, it is sufficient as long as the strand width is imaged by only one or two pixels 47 and all partially covered pixels 47 receive thermal radiation from both the strand 7 and the background 4.

[0140] Due to the slow strand speed, the strand generally cools down in the direction of the conveying material flow 2. For this application, special attention must be paid to Figure 7 Detailed information on gradient field design.

[0141] For the requirement of measuring the temperature of each strand 7 individually at a specified X position, the background 4 can be divided into individually temperature-controlled sections in the Y direction. This allows the infrared contrast minimum values ​​of all strands 7 to be set very close to the specified X position in all sections simultaneously, despite the presence of a temperature gradient along the strands 7 and the different average strand temperatures in the central section 4 b.

[0142] Smaller sections 51a and 51b can also be defined in the image in order to be able to determine in particular the temperature of the individual strands 7. Since the position of the strands 7 is not always fixed, it is advisable to use classical image processing in the infrared image and, in particular, to use threshold segmentation to define individual sections 51 around the individual strands or strand groups. The width of the sections 51 should be based on the respective width of the strands 7 in order to be able to maintain a stable relative object area density in each region of each section 51 for fluctuation evaluation.

[0143] If the strand temperature 26 is sufficiently stable in time, there is a simpler way to accurately determine the temperature of all strands 7 individually at a given X position. To this end, for a background 4 with a temperature gradient field 48, the average background temperature 25 is cyclically increased and decreased, and a narrow evaluation section 51 along the strand is defined for each strand 7 by a properly selected background area ratio. Since the background temperature 25 varies with time and location, the X position of the contrast minimum shifts in all sections 51 with the average background temperature 25, so that the object temperature 39 determined for each strand can be obtained at different X positions. Using regression analysis, the longitudinal temperature gradient of each strand 7 can be determined. The corresponding measurement result of the strand temperature 39 determined at the target measurement position X is calculated from the currently determined object temperature 39, the measurement position 41 of the fluctuation minimum, and is corrected by the product of the difference between the target position and the measurement position and the corresponding longitudinal temperature gradient of the strand 7.

[0144] Fig.10 An infrared sensor system 1 is shown on a wire material 7, similar to Fig. 8A , the system can also optionally have an enveloping thermostat 22. However, the environmental conditions here are more difficult, since the background 4 is immersed in the water bath 8 or at least flushed or sprayed with water. In very few system configurations, direct contact of water with the heated background 4 will work reliably for a long time. Deposits and flaking of deposits will result in an uncontrollable emissivity of the heated surface, making reliable background infrared emission impossible.

[0145] In the detailed view of the protective housing 10, which was developed for water contact, it can be seen that the temperature control device 6 in the form of a temperature control rod is thermally decoupled from the surrounding water. A heating and / or cooling element 21 is centrally mounted in the protective housing 10, which is monitored and temperature-controlled to the background temperature 25 by a temperature sensor 23; this heating and / or cooling element 21 radiates through the surface of the background 4 through the infrared-transparent window 11 towards the infrared sensor system 1. Infrared-transparent polymer films are known, for example, see the paper "Characterization of thin polymers for infrared windows" by Garrett Beals, Gregory Balonek, Corrie Smeaton and Joseph Sperry, published in the SPIE conference proceedings 12103 "Advanced Optics for Imaging Applications: UV through LWIR VII", paper number 1210309 (May 27, 2022); available at the following link: https: / / doi.org / 10.1117 / 12.2618378, which refers to such infrared-transparent polymer films. They can be connected to a suitably designed protective housing in a waterproof manner. Since the infrared-transparent window 11 absorbs part of the radiation emitted by the background 4, the internally arranged temperature control device 6 can be operated at a higher temperature, so that the background temperature 25 can be simulated based on the intensity evaluation of the infrared sensor system 1. For precise measurements, the infrared sensor system 1 can be calibrated in a similar measuring device using a calibration radiator. The temperature control of the temperature control device 6 can then be determined by transfer calibration.

[0146] Although the temperature control device 6 can set a strand-specific background temperature radiation 25 by means of a large number of heating and / or cooling elements 21 in the transverse direction of the strand 7, such an effort is hardly relevant for practical applications. Fig. 9 A comparable temperature gradient field can be more easily realized as a background radiation field. It is already possible to determine the statistical contrast using a single heating and / or cooling element 21, e.g. Fig. 9 As shown in the column area in Figure 2, this statistical contrast can be obtained by the temperature frequency distribution (Temperatur- By means of the frequency distribution, it can be determined whether the radiation emission of the background 4 is higher or lower than the radiation emission of the strand 7.

Claims

1. A method for contactlessly determining the temperature of linear and / or granular objects in a conveying material flow (2), in which method an infrared sensor system (1) is directed toward the conveying material flow (2) flowing in front of a background (4), and the temperature (26) of the linear or granular objects (3) is determined based on a measurement signal (29) of the infrared sensor system (1), characterized in that The temperature (25) of the background (4) is varied over time and / or location by means of a temperature control device (6), wherein the fluctuations (32) are determined for different background temperatures (25) based on the measurement signal (29) of the infrared sensor system (1) by means of an evaluation device (30), and the positions of the fluctuation minima are determined based on these fluctuations, wherein the object temperature (39) is determined based on the value of the measurement signal (29) at the time / location of the fluctuation minimum.

2. The method according to the preceding claim, wherein: The measurement signal (29) is subjected to regression analysis by a regression analysis module (33) of the evaluation device (30), wherein the functional relationship between the change of the fluctuation degree (32), in particular the fluctuation amplitude, and the background temperature (25) that changes with time and / or location is determined by the regression analysis module (33), and the time and / or location of the occurrence of the fluctuation minimum, in particular the amplitude minimum, is determined by the evaluation device (30) using the determined functional relationship, and the object temperature (39) is determined based on the value of the measurement signal (29) at the time / location of the fluctuation minimum determined according to the functional relationship.

3. The method according to the preceding claim, wherein: The background temperature (25) and / or the average measurement signal (29) and / or the reference temperature (38) are used as reference quantities for a functional relationship with the fluctuation degree (32), in particular the fluctuation amplitude, wherein for time and / or location partitions with the smallest fluctuation degree (32), the value of the reference quantity corresponds as closely as possible to the value of the background temperature (25) and the value of the infrared measurement signal (29), and for other time and / or location partitions, the reference quantity has a curve which is as linearly related as possible to the background temperature (25), the slope of which is proportional to the difference between the background temperature (25) and the object temperature (26).

4. The method according to any one of the two preceding claims, wherein: The reference temperature (38) is used as a reference variable for the regression, and the fluctuation (32) at the reference temperature (38) is determined and / or taken into account only when it is above or below the object temperature (26), so that the fluctuation (32) does not reach its minimum value, and the measured object temperature (39) is determined by extrapolation from the regression model (33), when the fluctuation (32), in particular the fluctuation amplitude, approaches zero or becomes smaller than a predetermined minimum fluctuation threshold.

5. The method according to any one of claims 2 to 4, wherein: In a further evaluation step, the time and / or location of the fluctuation minimum is determined, wherein in particular, a data record comprising the fluctuation degree (32) at different time and / or location evaluation zones (45), a reference temperature (38) and the corresponding time and / or location is used, wherein continuous data groups including fluctuation degrees less than a predetermined threshold are filtered out around the fluctuation degree (32), and for each data group, a regression of the time or location relative to the reference temperature (38) is performed, and for each data group, the measured object temperature (39) is inserted into the respectively determined regression equation, so that the time and / or location of the fluctuation minimum is determined.

6. The method according to any one of claims 2 to 5, wherein: The background temperature (25) is varied in a heating and cooling cycle, wherein in a heating half cycle the background temperature (25) is initially below the object temperature (26), reaches the object temperature and then exceeds the object temperature; the heating half cycle is followed by a cooling half cycle, in which the initially high background temperature (25) drops, then reaches the object temperature (26) again, then drops below the object temperature again and returns to the initial temperature, and at the same time, in a time and / or location evaluation zone (45) limited to a temperature window of the background temperature (25) and / or the average measured signal value (35) or a reference temperature (38), the fluctuation intensity (32) and the average background temperature (36) or the average measured signal value (35) or the reference temperature (38) calculated for the same zone are recorded quasi-continuously in a data memory, in particular a FIFO memory, wherein one to two minimum values ​​in the fluctuation intensity (32) are further processed depending on the recorded data, wherein for each new recorded data set the oldest recorded data set is no longer used for the evaluation and when a regression model is used, an updated determined object temperature (39) can be output at each measuring cycle.

7. The method according to any one of claims 2 to 5, wherein: The background temperature (25) is varied by a temperature control device (6) during the heating and cooling cycles so that the background temperature (25) never reaches the object temperature (26) and at the same time, in a time and / or location evaluation zone (45) limited to a temperature window of the background temperature (25) and / or the average measured signal value (35), the fluctuation intensity (32) and the average background temperature (36) or the average measured signal value (35) or the reference temperature (38) calculated for the same zone are recorded quasi-continuously in a data memory, in particular a FIFO memory, wherein the value of the fluctuation intensity (32) is further processed based on the recorded data for the lowest and highest background temperatures (25) in the transition section between the heating and cooling cycles and, when a regression model for extrapolation is used, an updated determined object temperature (39) is output at each measuring cycle.

8. A method according to any preceding claim, wherein: The thermal radiation field of the background (4) is changed over time and / or position by a temperature control device (6) so that at a specific time and / or at at least one specific position, a thermal image of the background (4) and a conveying material flow (2) flowing in front of the background (4) provided by the infrared sensor system (1) is evaluated by an evaluation unit (30) as at least approximately without contrast, wherein the object temperature (39) is determined based on the position at which the contrast is evaluated to be absent or the time at which the contrast is evaluated to be absent.

9. A method according to any preceding claim, wherein: The temperature of the background (4) is controlled by a temperature control device (6) so that a temperature gradient is generated along the conveying path of the conveying material flow (2). According to the temperature gradient, - the thermal radiation field of the background (4) has a temperature (25) in the central part (4b) of the background (4) which corresponds at least approximately to the temperature (26) of the object, a temperature in the upstream part (4a) which is lower than the temperature in the central part (4b), and a temperature in the downstream part (4c) which is higher than the temperature in the central part (4b) of the background (4), or - The thermal radiation field of the background (4) has a temperature (25) in the central part (4b) of the background (4) which at least approximately corresponds to the object temperature (26), a temperature in the upstream part (4a) which is higher than the temperature in the central part (4b), and a temperature in the downstream part (4c) which is lower than the temperature in the central part (4b) of the background (4).

10. A method according to any preceding claim, wherein: The background temperature (25) is increased or decreased over time or location to near the time or location average temperature by a temperature control device (6), and in addition, the time or location average temperature is changed or adjusted so that at the average temperature, the fluctuation amplitude (32) of the measurement signal (29) is close to zero.

11. A method according to any preceding claim, wherein: A product guide in the form of a tube is used as a background (4), which is rotated about its longitudinal axis into a contrast measurement position, in which a contrast measurement of the background (4) is performed by an infrared sensor system (1), wherein the contrast measurement is performed while the conveying material flow is continuously flowing or stopped.

12. A method according to any preceding claim, wherein: The measuring point (20) of the infrared sensor system (1) is moved along with the conveying material flow (2) by means of a rotating prism reflector (24) and / or is guided in the direction of the conveying path of the conveying material flow in front of a background (4).

13. The method according to the preceding claim, wherein: Based on the image evaluation, the rotation speed of the prismatic reflector (24) is readjusted so that the average size of the objects (3) displayed in the thermal image of the infrared sensor system (1) is minimized and / or the afterglow trail occurring in the forward and backward directions is minimized, so that individual object temperature measurements can be made and, if necessary, statistical reports on the temperature uniformity of the product flow can be prepared, wherein, preferably, the measuring point (20) moves at an at least almost constant scanning speed as the angular speed of the prismatic reflector (24) changes highly dynamically.

14. A method according to any preceding claim, wherein: An infrared sensor system (1) is used to determine the local object temperature and the position of the fluctuation minimum in multiple measuring sections (51) along the conveying path of a conveying material flow (2) so as to measure the temperature change of the object (3) and the path-dependent temperature change rate based on multiple measurements in the direction of the conveying material flow (2).

15. A method according to any preceding claim, wherein: The location-dependent temperature field of the background (4) also varies over time, and for the object (3), the positions of the fluctuation minima in the direction of the conveying material flow and the object temperature (39) determined at these locations are recorded in order to determine the path-dependent temperature change rate of the object (3) based on the point cloud obtained, for example by linear regression.

16. A method according to any preceding claim, wherein: In order to measure the temperature of the strands (7) individually, the infrared image is segmented using image processing methods and individual evaluation sections (51) are defined for individual strands (7) or groups of adjacent strands (7), in particular transversely to the direction of the conveying material flow, wherein the object temperature (39) is determined for each section and / or, in the case of a background field (4) that also changes over time, the temperature gradient in the longitudinal direction of the strand is also determined.

17. A method according to any preceding claim, wherein: The infrared sensor system (1) uses a plurality of sensor elements or a row or matrix of sensor elements to detect a plurality of measuring points (20) distributed along the direction of the conveying material flow simultaneously or successively.

18. A method according to any preceding claim, wherein: A temperature compensation (40) of an infrared sensor system (1) is determined using a positional and / or temporal situation when an object (3) has no contrast with a background (4).

19. A method according to any preceding claim, wherein: The infrared sensor system (1) operates within a predetermined temperature window even under fluctuating ambient conditions by means of an active temperature control device (5), preferably a water temperature controlled sleeve around the sensor head, the predetermined temperature window remaining constant regardless of ambient conditions.

20. A method according to any preceding claim, wherein: In a calibration step, the infrared sensor system (1) is repositioned from the intended measurement position on the background (4) to a calibration station having an at least approximately blackbody radiator, the temperature of which at the measurement point is adjusted to an operating point temperature associated with the object (3) to be measured, wherein the repositioning is preferably performed without interrupting the power supply and temperature control, wherein the calibration step comprises a plurality of sub-steps, namely firstly aligning the infrared detector to the blackbody radiator of the calibration station and calibrating it to the associated operating point by means of a first parallel measurement of the infrared signal and the calibration reference temperature, and before the absolute operating point calibration Afterwards, a transfer calibration is performed on the background (4), wherein the background (4) is set to a temperature that can be at least approximately stabilized to the same operating temperature as the blackbody radiator reference, wherein a second parallel measurement is then performed with the infrared sensor system (1) repositioned to the measurement position, in which the infrared radiation of the background (4) is measured simultaneously and the background temperature (25) is measured by means of a contact temperature sensor (23), wherein the emissivity of the temperature-controlled background environment is determined as a near-blackbody radiator based on the result of the second parallel measurement and is stored as a calibration parameter for this operating point.

21. A device for non-contact temperature measurement of linear or granular objects (3) in a conveying material flow (2), comprising: An infrared sensor system (1) for detecting the radiation field of a conveying material flow (2) flowing in front of a background (4); A temperature control device (6) for controlling the temperature of a background (4), wherein, in particular, conditions for measuring with inclusions of gloss can be generated by the environment; and an evaluation device (30) for evaluating a measurement signal (29) of an infrared sensor system (1) and determining an object temperature based on the measurement signal (29), characterized in that the temperature control device (6) is configured to change the temperature of the background (4) over time and / or over a region, wherein the evaluation device (30) is configured to evaluate the degree of fluctuation of signal fluctuations in the measurement signal (29) of the infrared sensor system (1) detected under a changing background temperature (25), and to determine the time and / or region of a fluctuation minimum and to determine the measured object temperature (39) based on the value of the measurement signal (29) at the time / region of the fluctuation minimum.

22. The device according to the preceding claim, wherein The evaluation device (30) has a regression analysis module (33), which is suitable for establishing a functional relationship between the fluctuation degree (32), especially the fluctuation amplitude, and time or location through regression analysis, and based on this functional relationship, it is possible to determine the time or location of the occurrence of the fluctuation minimum, especially the amplitude minimum.

23. The device according to the preceding claim, wherein In the evaluation device (30), the boundaries of time and / or location evaluation zones (45) with approximately very similar background temperatures (25) are defined, the evaluation zones preferably being characterized by temperature windows or time windows or background temperatures (25) within the image surface area, wherein the evaluation device (30) is preferably designed to calculate the following data for each of these evaluation zones (45) for subsequent analysis and to at least temporarily store these data: - an optionally transformed fluctuation (32) of the measurement signal (29), which is preferably quantified by evaluating the amplitude, range, cutoff range and / or standard deviation, a representative temperature reference value, in particular of the background temperature (25), the average measurement signal (35) or the reference temperature (38), selected for the evaluation zone (45) or calculated by averaging or filtering, wherein for the time and / or location zones with the smallest fluctuations (32), the value of the representative temperature reference value corresponds as closely as possible to the value of the background temperature (25) and the value of the infrared measurement signal (29), and for the other time and / or location zones, the representative temperature reference value has a curve which is as linear as possible with respect to the background temperature (25), the slope of the line of which is proportional to the difference between the background temperature (25) and the object temperature (26), a representative value for the evaluation zone (45) selected in time or calculated by averaging or filtering, which value is preferably characterized by the average value of the start time and the end time of the data recording of this evaluation zone (45), - a value or values ​​selected in time or calculated by appropriate averaging or filtering and retained for later refined location analysis and / or contours defining an evaluation zone (45).

24. The device according to any one of claims 21 to 23, wherein: The temperature control device (6) is configured to generate a temperature gradient along the conveying path of the conveying material flow (2), according to which the temperature gradient - the thermal radiation field of the background (4) has a temperature (25) in a central part (4b) of the background (4) which corresponds at least approximately to the object temperature (26), a temperature in an upstream part (4a) which is higher than the temperature in said central part (4b), and a temperature in a downstream part (4c) which is lower than the temperature in said central part (4b) of the background (4), or - the thermal radiation field of the background (4) has a temperature (25) in a central part (4b) of the background (4) which at least approximately corresponds to the object temperature (26), a temperature in an upstream part (4a) which is lower than the temperature in said central part (4b), and a temperature in a downstream part (4c) which is higher than the temperature in said central part (4b) of the background (4).

25. The device according to any one of claims 21 to 24, wherein A product guide in the form of a tube is provided as background (4), which tube can be rotated about its longitudinal axis into a contrast measurement position.

26. The device according to any one of claims 21 to 25, wherein The environment of the measurement zone, in particular the environment of the zone that can be indirectly detected by the infrared sensor system (1) through the angular reflection of gloss on the surface of the object (3), emits slightly more infrared radiation through the housing temperature controller (22) than the infrared radiation of the object (3) having the measured object temperature (39), so as to compensate for the infrared radiation losses in the edge area and the measuring hole (19), and in the measurement zone, glossy measurement conditions can be generated to a good approximation, thereby minimizing the influence of the infrared emissivity ε of the object (3).

27. The device according to any one of claims 21 to 26, wherein The background (4) and / or the inner wall of the housing temperature controller (22) is provided with a coating, and the emissivity of the coating relative to infrared radiation is greater than 40% or greater than 70% or greater than 85%.

28. Device according to the preceding claim, wherein The inner wall of the background (4) and / or the housing thermostat (22) is provided with a non-stick coating made of fluoropolymer or silicone.

29. The device according to any one of claims 21 to 28, wherein The infrared sensor system (1) comprises a plurality of measuring points (20) along a conveying path of a conveying material flow (2) and / or is capable of determining the local object temperature in a plurality of evaluation sections (51).

30. The device according to any one of claims 21 to 29, wherein: The infrared sensor system (1) comprises a rotatably driven prismatic reflector (24) for moving a measuring point (20) together with a conveying material flow (2) and / or for guiding the measuring point (20) in the direction of a conveying path of the conveying material flow (2) in front of a background (4).

31. The device according to the preceding claim, wherein The control device (30) for controlling the rotation speed of the prismatic reflector (24) based on image evaluation is designed so that the average size of the objects (3) displayed in the thermal image of the infrared sensor system (1) is minimized and / or the afterglow tails occurring towards the front and rear are minimized and / or the measuring point (20) is moved at an at least almost constant scanning speed with highly dynamic changes in the angular speed of the prismatic reflector (24).

32. The device according to any one of claims 21 to 31, wherein The infrared sensor system (1) comprises a plurality of sensor elements or a row or matrix of sensor elements having a plurality of measuring points (20) distributed along the direction of a conveying material flow.

33. The device according to any one of claims 21 to 32, wherein: An active temperature control device (5), preferably a water temperature control sleeve around the sensor head, is provided for controlling the temperature of the infrared sensor system (1) within a predetermined temperature window even under fluctuating ambient conditions, while the predetermined temperature window remains constant regardless of the ambient conditions.

34. A granulating device for granulating plastics, pharmaceuticals or foods, comprising a device for contactless temperature determination constructed according to any one of claims 21 to 33.

35. A granulation device according to the preceding claim, comprising an underwater granulator (13) and a granulation dryer (17) arranged downstream of the underwater granulator, wherein: An infrared sensor system (1) of a device for contactless temperature determination is directed toward a conveyed material flow (2) at a dryer outlet (18) of a granulate dryer (17).

36. The granulation device according to claim 34, comprising a strand granulation head for producing strands, wherein: The infrared sensor system (1) of the device for contactless temperature determination is directed towards the strand (7) as it leaves the strand pelletizing head.

37. Granulation device according to the preceding claim, wherein The temperature control device (6) is designed to control the temperature of a background (4) located behind a linear object (3) which is guided by water or surrounded by a water flow only in a narrow transverse band, so that the infrared emission evaluated by the sensor corresponds to the infrared emission of the desired background temperature (25).

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