Measuring device

Abstract

The utility model relates to measuring equipment, which is used for determining the concentration of components in fluid, such as a cooling lubricant or HFC hydraulic fluid through a refraction measurement method, and is characterized in that the fluid to be used for measurement is guided to pass through a sample cavity (10), the sample cavity is connected to a fluid inlet (12) and a fluid outlet (14), and the fluid inlet (12) and the fluid outlet (14) are communicated with each other. And the sample chamber is at least partially transparent such that a beam, preferably in the form of a light source of a laser (22), passing through the sample chamber (10) together with the fluid, is at least partially refracted (n) and can be detected by a sensor device (26) outside the sample chamber (10).

Description

Technical Field

[0001] The utility model relates to a measuring device, which is used for determining the concentration of components in a fluid, such as a cooling lubricant or an HFC hydraulic fluid, by means of a refractometry method. Background Art

[0002] DE 10 2010 028 319 A1 discloses a method for controlling the concentration of a cooling lubricant mixed with water in a machine tool, together with an associated device, which measures both the refractive index and the electrical conductivity of the cooling lubricant mixed with water by refractometry, combines the two measured values ​​into a control variable, and replenishes water and / or cooling lubricant if the control variable deviates from a setpoint value. To determine the refractive index of the cooling lubricant mixed with water, the device uses digital refractometry, which has an LED as a light source and a CCD sensor as a detector. Utility Model Content

[0003] Starting from the prior art, the object of the present invention is to provide a relatively improved measuring device with which a plurality of disturbance variables that may occur during measurement can be compensated.

[0004] A measuring device according to the invention achieves this object in its entirety.

[0005] By guiding the fluid to be measured through a sample chamber connected to a fluid inlet and a fluid outlet, and by making the sample chamber at least partially transparent so that the radiation of a light source, preferably in the form of a laser, which passes through the sample chamber along with the fluid, is at least partially refracted and can be detected by a sensor device outside the sample chamber, a partial separation of the light source, sample chamber, and sensor device is achieved. This creates numerous adjustment and correction options, allowing the measuring device to be used for various measurement tasks and calibrated accordingly. Because the fluid to be studied is guided through the sample chamber, the sample is also decoupled from the actual measuring device, which consists of the light source and sensor device, allowing for undisturbed measurements independent of the actual supply circuit for the hydraulic consumer. A light source in the form of a laser is preferably used, which, compared to conventional LED technology, enables collimation, i.e., parallel alignment of the otherwise diverging light beam. This results in improved measurement value resolution for sensor devices, which typically consist of photodiode arrays, also known as "diode arrays."

[0006] Lasers also allow the introduction of higher radiation powers, so that even if the fluid is turbid and / or the sample chamber, which remains partially transparent, is contaminated, at least reliable measured value detection is ensured.

[0007] In a preferred embodiment of the measuring device according to the invention, the sample chamber, on the side facing the sensor device, is bounded by a light-transmissive wall in the form of a glass wall, and the light source is accommodated in a receiving chamber of the device housing of the measuring device, through which the fluid at least partially flows before entering the sample chamber. It has proven advantageous to generate turbulence in the fluid as it flows through the sample chamber. This is important for washing away contamination of the sample chamber's glass wall and for at least replacing the sample fluid in the measurement or sample chamber.

[0008] Preferably, the light source emits light at an oblique angle, preferably 40°, to the direction of fluid flow in the sample chamber, and the surface extension of the sensor device and its position relative to the light source are selected such that light beams impinging on the sensor device at different angles during transmitted light can be detected. This allows the refractometer to be operated using transmitted light dependent on the light source, depending on the measurement task, without requiring major modifications to the measuring device itself.

[0009] In another preferred embodiment of the measuring device according to the present invention, the sensor device is part of a sensor chamber of a sensor housing, and the chamber sensor, which is filled with gas, preferably air, forms a spatial distance between the sample chamber with its light-transmissive walls and the sensor surface of the sensor device. In this case, preferably viewed in an imaginary vertical projection, the light source is preferably located only at the beginning of the sample chamber, and the starting point of the sensor device is located at the end of the sample chamber. Thus, by appropriately selecting the spatial distance and the correspondingly selected projection surface for the arrangement of the sensor device, it can be adjusted both vertically and horizontally to thereby adapt the sensitivity or measuring range.

[0010] In order to ensure a preferably turbulent fluid course, a fluid channel having individual channel sections is at least partially provided in the supply housing between the fluid inlet and the fluid outlet, so that a turbulent flow through the sample chamber occurs due to multiple deflections.

[0011] In another preferred embodiment of the measuring device according to the present invention, the overall housing of the device is assembled from individual housing components, including a supply housing with components for the fluid channel, the device housing with the light source, and a sensor housing with the sensor device. The multi-housing component design allows for rapid disassembly and reassembly of the measuring device for maintenance and cleaning. This also implements a building block principle for the overall housing, which, in practice, facilitates retrofitting the measuring device according to the present invention to an already supplied and operating hydraulic system.

[0012] In another preferred embodiment of the measuring device according to the invention, the measuring device is connected via a switchable valve to a pressure supply, such as a hydraulic pump, which draws its fluid from a reservoir tank and hydraulically supplies a processing machine as a consumer. The pressure supply device is connected with its input side via a branch to the fluid line between the hydraulic pump and the switchable valve, and the output side of the processing machine opens at a branch point into a return line that is connected to a fluid outlet in the supply housing and leads to the reservoir tank. This allows the measuring device to be decoupled from the actual pressure supply for the hydraulic consumer in the bypass, allowing measurements to be performed at discrete time intervals outside of the operation of the hydraulic consumer. For this purpose, a further switching valve is preferably connected to the section of the return line between the fluid outlet in the supply housing and a further branch point into which the output side of the processing machine opens.

[0013] In another preferred embodiment of the measuring device according to the present invention, a third on-off valve and a fourth on-off valve are connected to the inflow line to the fluid inlet and the return line from the fluid outlet, respectively, and are used to introduce or remove a cleaning medium. This allows the measuring device to be cleaned of contamination by means of a cleaning process, regardless of the operation of the processing machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The measuring device according to the present invention will be explained in detail below with the aid of an embodiment and a measuring method to be implemented using the measuring device. In this case, in the drawings which are schematic and not shown to scale:

[0015] Figure 1 A longitudinal section showing the main components of the measuring device;

[0016] Figures 2 to 5 Shows different possibilities for carrying out measurements according to the transmitted light principle;

[0017] Figure 6 、 Figure 7 and Figure 8 Different types of operation of the measuring device are illustrated with the aid of a flow chart;

[0018] Figure 9 A type of hydraulic circuit diagram showing the integration of the measuring device into the hydraulic measurement and supply circuit; and

[0019] Figure 10 One type of operation of the measuring device is illustrated with the aid of a flow chart. DETAILED DESCRIPTION

[0020] exist Figure 1 The measuring device, shown with its main system components, is shown in a typical operating state. The measuring device is used to determine the concentration of components in fluids, such as cooling lubricants or HFC hydraulic fluids, by refractometry. Hydraulic fluids are commonly used in fluid technology to transfer energy in the form of volume flow and / or pressure to hydraulic systems. These hydraulic oils are typically based on mineral oil with appropriate additives. HFCs are highly flammable hydraulic fluids and typically contain water glycol and polyethylene glycol solutions with a water content exceeding 35%. These HFC hydraulic fluids are typically used in hard coal mining and civil aviation. These hydraulic fluids are also notably used in military vehicles, such as armored vehicles, which may be exposed to hostile fire. Cooling lubricants or cooling lubricants reduce friction through lubrication and, therefore, reduce tool wear, workpiece heating, and energy requirements during cutting operations. In both cases, a specified concentration of HFC and cooling lubricant is maintained to ensure reliable operation. The measuring device according to the present invention is used to maintain the corresponding concentration.

[0021] The fluid to be measured by means of the measuring device is guided through a sample chamber 10 which is connected to a fluid inlet 12 and a fluid outlet 14. Possible flow directions are Figure 1 The inlet 12 and the outlet 14 are indicated here by arrows. The fluid inlet 12 and the fluid outlet 14 are both connected to a fluid supply circuit 16 in a conventional manner, as shown in FIG. Figure 9 Depicted in.

[0022] The original sample chamber 10 defines a rectangular parallelepiped volume with a flat extended structure and extends toward Figure 1From the top, the sample chamber 10 is bounded by a light-transmissive glass wall 18, typically consisting of a thin-walled rectangular glass plate. The sample chamber 10 is delimited on the outer periphery by square sealing rings upward and downward relative to the adjacent housing components of the measuring device, thereby reliably preventing undesired escape of fluid from the sample chamber 10 into the surrounding environment. A laser 22 is laterally connected to the sample chamber 10 and incorporated into the device housing 20 of the measuring device. Its upper laser emission surface faces toward the sample chamber 10 and projects into an inclined channel 24 that guides the fluid. The beam of the light source (here, in the form of the laser 22) thus traverses the sample chamber 10 containing the corresponding fluid, thereby receiving a first refraction n, as will be explained in more detail below. The refracted beam is detected by a sensor device 26 outside the sample chamber 10. The sensor device 26 comprises a photodiode array, also known as a diode array, as a light-sensitive sensor. In this context, CCD sensors can also be used, but also CMOS sensors, which as light-sensitive electronic components are based on internal light effects and are freely available on the market in many embodiments.

[0023] If also from Figure 1 As can be seen, the light source in the form of a laser 22 is statically accommodated at one end in an associated receiving chamber 28 in the device housing 20, so that before the fluid enters the actual sample chamber 10, the outlet cross section for the laser beam is flowed through by the fluid, which flows from the horizontally extending line section 30 into the inclined channel 24 parallel to the longitudinal orientation of the sample chamber 10. The line section is arranged in a manner such that the fluid flows in parallel to the longitudinal orientation of the sample chamber 10. Figure 1 The right side of the pipe is closed by a plug 32 and the pipe sections 34 and 36 extending vertically from the bottom lead into the relevant horizontal pipe section 30, which extends in the direction of the pipe. Figure 1 The horizontal line section 30 continues to the right behind the stopper 32 and opens into a vertical line section 36, to which the fluid outlet 14 is connected. Conversely, the fluid inlet 12 opens into the vertical line section 34 from the left to transport the fluid into the sample chamber 10. Exiting the vertical line section 36, the horizontal line section 30 continues to the right and is closed there by a sensor 38, which can, for example, be a measuring device for parameters such as pressure, temperature, viscosity, pH, or conductivity. A sensor 38 capable of measuring two or more different such parameters can also be used. Temperature measurement is particularly necessary for temperature compensation within the context of refractometry.

[0024] If you can also Figure 1As can be seen from the results, the light source in the form of a laser 22 emits light at an angle of approximately 40° to the horizontally extending fluid flow direction in the sample chamber 10. The rectangular surface extension of the sensor device 26 is selected in its position relative to the light source so that the light source is preferably surrounded by the sensor device 26 over the entire circumference, both in the transmitted light method preferred here and also when the light beam is incident at different angles, possibly in a grazing manner. In order to calibrate the measuring device and in particular to adapt the sensor device 26 to the actual measurement situation within the measuring device, the measuring device is based on Figure 2 The illustration can be arranged not only horizontally but also vertically relative to the light emission point of the laser 22. For this purpose, it is sufficient to loosen and retighten the screws of the adjustment device 40, to which the sensor device 26 is fixed and by means of which the sensor device can be positioned relative to the fixedly arranged sensor housing 42. In this regard, the sensor housing 42 is connected to the upper side of the device housing 20 as a component of the overall housing. In particular, the plate-shaped sensor device 26 opens into a square sensor cavity 44 of the sensor housing 42, which can be provided with gas and thus fill the spatial distance between the sample chamber 10 with its light-transmissive wall 18 and the exposed sensor surface 46 of the sensor device 26. For a simpler illustration, in Figure 1 The laser 22 and the sensor in the form of the device 26 and the corresponding measuring device 38 are shown without the associated wiring. Depending on the wavelength and the refractive index range at which the sensor device 26 is to be supplied, other working gases, for example in the form of xenon, can also be accommodated in the sensor chamber 44 instead of air. Figure 1 As seen in an imaginary vertical projection within the drawing plane, the light source in the form of laser 22 is arranged at the beginning of sample chamber 10, and the starting point of sensor device 26 is arranged at the end of sample chamber 10. This results in particularly good measurement value detection over the entire area, and the inclined arrangement of laser 22 produces a good diffraction pattern or interference pattern when penetrating the fluid in sample chamber 10. Furthermore, due to the oblique angle of incidence of the laser beam on sensor surface 46, the installation space for sensor housing 42, and therefore for the entire measuring device, can be kept small, allowing the measuring device to be installed even in tight space conditions. This also simplifies the retrofitting of existing installations with the measuring device.

[0025] The channel sections 34, 36 extending between the fluid inlet 12 and the fluid outlet 14 are at least partially configured as a fluid channel 48 in the supply housing 50. The overall housing of the device is thus assembled from individual housing components, in particular the supply housing 50 comprising the components with the fluid channel 40, the device housing 20 with the light source (here in the form of a laser 22), and the sensor housing 42 with the sensor device 26. This results in a modular design of the overall housing for the measuring device, which allows the measuring device to be connected to different machines and system components by adapting the individual components.

[0026] As mentioned at the outset, the measuring device is part of a fluid supply circuit 16, which can be connected to a pressure supply device, such as a hydraulic pump P1, via a switchable valve V1. The motor-driven hydraulic pump P1 draws fluid, such as a cooling lubricant or HFC fluid, from a reservoir tank CM1 and hydraulically supplies it to a typical processing machine BM as a consumer. The processing machine BM is connected on its inlet side via a branch to the fluid line between the hydraulic pump P1 and the switchable valve V1. The outlet of the processing machine BM, in turn, opens at another branching point 54 into a return line connected to the fluid outlet in the form of a fluid outlet 14 in the supply housing 50 of the measuring device and leads to the reservoir tank CM1. A further switchable valve V2 is provided in the aforementioned section of the return line between the fluid outlet 14 in the supply housing 50 and the further branching point 54, into which the outlet of the processing machine BM flows. Furthermore, a third switching valve V3 and a fourth switching valve V4 are connected to the inflow line to the fluid outlet 12 and the return line from the fluid outlet 14, respectively, for introducing the cleaning medium DL into or out of another storage tank CM2.

[0027] A control line 56 for transmitting measurement data extends between the processing machine BM and a measuring device, the housing of which is located at Figure 10 The housing parts 20, 42 and 50 are shown in FIG. 1 , and the control lines can realize the cleaning process according to the machine status and / or the measuring device status. The measured parameter detection at least partially realized by the sensor 38 transmits its measured data via an additional measuring line 56 to a processor control system 59 (not shown in detail) as a higher-level system, as shown in FIG. Figure 10 In addition to the usual measured values ​​of pressure, temperature and viscosity, there is also the possibility of measuring the pH value of the fluid and its conductivity via sensor 38 or other sensors 1, 2, ... x (not shown). Figure 9Starting from another control line 60, the measuring device can control another fluid pump P2, which, when necessary, extracts the missing concentrate detected by the measuring device from the concentrate container CM3. The liquid level in the concentrate container CM3 is monitored by a liquid level switch 62, which is coupled to the processor control system 59 of the measuring device by means of another measuring line 64. If, within the scope of the refractometry performed by means of the measuring device, it is to be determined that a lubricant component is missing in the cooling lubricant supply for the processing machine BM or that HFC is missing in the supply of HFC hydraulic fluid, the missing component can be introduced into the storage tank CM1 via the concentrate container CM3 by controlling the supply pump P2, and the correctly enriched cooling lubricant amount or HFC fluid reaches the processing machine BM again, and the refractometry measurement is continued within the enrichment scope by means of the measuring device. Figure 10 The actuators denoted by external actuators 1 , 2 , . . . y in this case are in particular components P1 and P2 and valves V1 , V2 , V3 , V4 etc.

[0028] If dirt occurs, in particular with respect to the sample chamber 10, the supply circuit 16 can be blocked by means of valves V1, V2 and the sample chamber 10 can be cleaned by introducing a suitable cleaning medium DL, including compressed air, by opening valves V3 and V4, and thus the dirt particles can be washed away, which are then collected in the storage tank CM2 for further processing or disposal. After the cleaning process has been carried out, the valves V3 and V4 can then be returned to their original positions in a spring-loaded manner. Figure 9 In the initial position shown in , ie, moved into its blocking position and after reopening valves V1 and V2 , the measuring device is used again for refractometric measurements with the fluid supply circuit 15 connected.

[0029] The measuring device according to the invention is explained in more detail below with reference to the associated measuring method. Figure 2 Here, the principle of such a measurement based on the transmitted light principle is shown. Figure 1 The laser 22 shown in FIG. 7 emits a collimated laser beam 70 which undergoes a first refraction n1 at the boundary surface of the sample chamber 10 to the plate-shaped glass wall 18. A second refraction n2 then takes place at the glass wall 18 in the form of a conventional glass plate. Figure 2 The signal curve of the linear array or sensor surface 46 in liquids of different concentrations is described. If a vertical adjustment is to be made by changing the vertical distance between the sensor surface 46 and the glass wall 28, an adjustment possibility for the sensitivity is obtained. If the sensor surface 46 can be moved horizontally, the measurement value range can be adjusted. Figure 2In the principle diagram of the measured value detection together with the curve shown, a homogeneous fluid in the sample chamber 10 is investigated, but turbid fluids can also be examined. This is possible in principle because laser diodes or lasers 22 with different intensities can be controlled by a control and / or regulating device (not shown in detail) in the form of a processor control system 59. However, it is preferred that the laser 22 adjusts its intensity autonomously.

[0030] exist Figure 3 In the example shown in FIG, the measured value curve of the turbidity of the fluid in the sample chamber 10 is shown, the thick solid measured value curve shows the initial measured value curve, and the thin measured line relates to the intensity loss due to the turbidity of the fluid. In order to re-reach the earlier peak detection despite the intensity loss, according to Figure 3 The thick solid curve shown requires adaptation of the laser 22, for example within the scope of adapting the duty cycle or discharge ratio (also known in technical terms as "duty cycle"), or by increasing the current intensity for the laser diode. Another adaptation possibility is to change the image refresh rate or refresh rate, also known in technical terms as shutter frequency, of the photodiode array or diode array in the form of the sensor device 26. The relevant adaptation of the laser intensity or the detector sensitivity with respect to the possible turbidity of the fluid present in the sample chamber 10 is shown, for example, in Figure 6 In order to carry out the relevant setting cycle, at least as an input prerequisite, a peak value determination is carried out as a reference, i.e., a peak value for the light received by refraction on the photodiode array in the form of the sensor device 26 is predetermined when using a fluid in the sample chamber 10 that is to be uniformly transparent to light, as in Figure 2 The actual refraction of turbidity in the case of including output value is based on Figure 7 The diagram results from the measured variable detection in terms of the duty cycle and current intensity for the laser 20, including the determination of the shutter frequency of the diode array of the sensor device 26. In this way, interference variables arising from turbidity can be compensated within the scope of conventional measurements.

[0031] In addition to the aforementioned turbidity, according to Figure 4 As shown in the figure, other possible interfering variables may also occur in the fluid of the sample chamber 10, such as contamination in the form of finely dispersed particles 72, such as may usually occur in emulsions, or in the form of larger particles 74 including air bubbles in the moving volume flow within the sample chamber 10. Figure 4The leftmost portion of the figure shows how the measured value curve, formed by the broad intensity increase caused by laser light scattering by finely dispersed particles 72 in the fluid flow, is derived, starting from the average peak 78 of the measured value curve with zeros rounded off, within the context of the typical refraction n1 by the fluid and the typical refraction n2 by the glass pane. A clear distinction is made between the brief, sharply angled peaks of varying intensity caused by the particles 74 or bubbles mentioned, which result from the altered refraction. Relevant interfering variables can also be compensated for by their individual detection and do not interfere with the determination of the concentration of the fluid used using the measuring device.

[0032] according to Figure 5 The diagram of in turn relates to different disturbance variables within the scope of concentration measurement, wherein transparent planar dirt with a changed refractive index n3 appears on the glass wall 18 with a refractive index n2. Figure 5 The peak curve on the sensor surface 46 (diode array) is shown by a dashed line (without dirt 82), and the right curve shows the evaluation with dirt applied to the glass pane 18. Figure 5 The two peak curves of the same measured value magnitude shown in are shifted horizontally by a value Δx, which can be evaluated and thus allows inferences to be drawn about the extent of contamination 42 on the glass pane 18. In this respect, these disturbance variables can also be recalculated within the context of determining the fluid concentration.

[0033] In all the above-mentioned interfering variables such as the turbulence of the fluid, particle contamination or impurities of the glass wall 108, the above-mentioned Figure 9 The cleaning process described in Figure 8 Here, the measuring and cleaning process can be carried out in principle as follows:

[0034] AUF = Flow to the measuring device is established by opening valves V1 and V2.

[0035] MES = Measurement 1 at a defined time (fluid = cooling lubricant or HFC)

[0036] ZU = Stop the inlet flow to the measuring device by closing valves V1 and V2

[0037] SP1 = Start the cleaning process by opening valves V3 and V4

[0038] = Clean the sample chamber 10 at a certain time

[0039] SP2 = Terminate the cleaning process, valves V3 and V4 remain open

[0040] KAL = measurement 2 is carried out at a certain time (fluid = cleaning fluid, water or ventilation)

[0041] AUS = Evaluate measurement 2 in KAL and signal (measurement ok, recalibration, maintenance required)

[0042] SP3 = Close valves V3 and V4

[0043] The aforementioned refractometer for measuring the concentration of a coolant, lubricant, HFC fluid, or other fluid whose component concentrations are to be monitored performs individual, discrete measurements. The refractive index for determining the coolant concentration is between 0 and 25% Brix (refractive index value), and the refractive index for determining the HFC concentration is between 30 and 50% Brix. Within the scope of self-diagnosis, the sensor system 26 can be regularly internally checked for the validity of the measured data. If, for example, a peak (hot spot) cannot be detected on the diode array or sensor surface 46 due to excessive turbidity in the fluid, the sensor system 26 should no longer emit measured values, and this should be indicated via the status of the sensor system 26.

[0044] Furthermore, the measuring device enables so-called online calibration. After cleaning the sample chamber 10 or the measuring cell, a reference measurement is performed in water or air. If a deviation from the expected value with the cleaning fluid is measured, the sensor device 26 is automatically recalibrated. For this purpose, the measured value with the cleaning fluid is used as the new zero point. In addition, a warning "clean refractometer" or similar is issued. By evaluating the deviation from the initial value at startup, it is also possible to determine the correct calibration according to the actual conditions. Figures 2 to 5 The embodiment of the invention foresees the replacement of the laser 22 and / or the glass wall 18 in the form of damage to the glass pane. This therefore has no counterpart in the prior art.

Claims

1. A measuring device for determining the concentration of a component in a fluid by refractometry, characterized in that A fluid to be measured is guided through a sample chamber (10), which is connected to a fluid inlet (12) and a fluid outlet (14) and is at least partially transparent, so that a radiation beam of a light source, which passes through the sample chamber (10) together with the fluid, is at least partially refracted (n) and can be detected by a sensor device (26) outside the sample chamber (10).

2. The measuring device according to claim 1, characterized in that The fluid is a cooling lubricant or an HFC hydraulic fluid.

3. The measuring device according to claim 1, characterized in that The light source is in the form of a laser (22).

4. The measuring device according to claim 1, characterized in that The sample chamber (10) is delimited on its side facing the sensor device (26) by a light-transmissive wall, and the light source is accommodated in a receiving chamber (28) of a device housing (20) of the measuring device, through which the fluid at least partially flows before entering the sample chamber (10).

5. The measuring device according to claim 4, characterized in that The light-transmitting wall is in the form of a glass wall (18).

6. The measuring device according to any one of claims 1 to 5, characterized in that The light source emits light at an oblique angle to the direction of flow of the fluid in the sample chamber (10), and the surface extension of the sensor device (26) and its position relative to the light source are selected so that the sensor device (26) can detect the light beam not only in the case of transmitted light but also when the light beam is incident in a grazing manner at different angles.

7. The measuring device according to claim 6, characterized in that The inclination angle is 40°.

8. The measuring device according to any one of claims 1 to 5, characterized in that The sensor device (26) is part of a sensor chamber (44) of a sensor housing (42), which is filled with gas and creates a spatial distance between the sample chamber (10) with its light-transmissive walls and a sensor surface (46) of the sensor device (26).

9. The measuring device according to claim 8, characterized in that The gas is air.

10. The measuring device according to any one of claims 1 to 5, characterized in that As seen in an imaginary vertical projection, the light source is arranged at the beginning of the sample chamber (10) and the starting point of the sensor device (26) is arranged at the end of the sample chamber (10).

11. The measuring device according to any one of claims 1 to 3, characterized in that A fluid channel (48) extends at least partially in a supply housing (50) between the fluid inlet (12) and the fluid outlet (14), the fluid channel having individual channel sections (34, 36).

12. The measuring device according to claim 4 or 5, characterized in that A fluid channel (48) extends at least partially in a supply housing (50) between the fluid inlet (12) and the fluid outlet (14), the fluid channel having individual channel sections (34, 36).

13. The measuring device according to claim 12, characterized in that The overall housing of the measuring device is assembled from individual housing parts, which include a supply housing (50) with components of the fluid channel (48), the device housing (20) with the light source, and a sensor housing (42) with the sensor device (26).

14. The measuring device according to claim 11, characterized in that The measuring device is connected via a switchable valve (V1) to a pressure supply device, which draws its fluid from a reservoir tank (CM1) and hydraulically supplies a processing machine (BM) as a consumer. The pressure supply device is connected with its input side via a branch to a fluid line between the pressure supply device and the switchable valve (V1), and the output side of the processing machine (BM) leads at a branch point (52) to a return line, which is connected to a fluid outlet (14) in the supply housing (50) and leads to the reservoir tank (CM1).

15. The measuring device according to claim 14, characterized in that The pressure supply device is a hydraulic pump (P1).

16. The measuring device according to claim 14, characterized in that A further switching valve (V2) is connected in the section of the return line between the fluid outlet (14) in the supply housing (50) and a further branching point (54), into which the output side of the processing machine (BM) opens.

17. The measuring device according to any one of claims 1 to 5, characterized in that A third switch valve (V3) and a fourth switch valve (V4) are respectively connected to the inflow pipeline leading to the fluid inlet (12) and the return pipeline from the fluid outlet (14), and the third switch valve and the fourth switch valve are used to introduce or export the cleaning medium (DL).

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