Method for determining the density of at least a viscous, particularly liquid, sample - Patents.com

Abstract

To provide a method for determining density of a sample which is at least viscous and is specifically liquid by using a rotary rheometer.SOLUTION: A rheometer 100 includes: a first measurement unit 7 for containing a sample 12 which is at least viscous and is specifically liquid; and a second measurement unit 8 immersed in the sample 12. The first measurement unit 7 and the second measurement unit 8 are capable of making a relative motion to each other and a second measurement unit 8 has a known volume V. A method includes the steps of: measuring perpendicular resistance between measurement units 7 and 8 after the second measurement unit 8 is immersed in the sample 12, the measured perpendicular resistance corresponding to buoyance between the sample 12 and the second measurement unit 8; and calculating density of the sample 12, using the known volume of the second measurement unit 8 and the measured resistance, on the basis of the principle of Archimedes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to a method for determining the density of at least a viscous, in particular liquid, sample by means of a rheometer according to claim 1 and to a rheometer for carrying out said method according to claim 10. [Background technology]

[0002] Various rheometers are known from the prior art for determining the rheological properties of viscous, in particular liquid, samples. However, a disadvantage of the known rheometers is that the density of the sample to be examined cannot be determined in situ, i.e. directly in the rheometer during the process of determining the rheological properties of the sample to be examined. To determine the density of a viscous or liquid sample, the sample must be introduced into an external density measuring device that is separate from the rheometer. Various density measuring devices are known from the prior art, in one example in the form of a balance, in which the distance value is measured when a measuring body is immersed in the liquid sample. Based on this measured distance, it is then possible to determine the density of the liquid sample. However, it is only possible to subsequently remove the sample to be examined in order to carry out a density measurement by interrupting the experiment in the rheometer.

[0003] The inability to measure the density of a viscous, especially liquid, sample directly in conjunction with or during the measurement of its rheological properties is a major drawback, particularly when the rheological measurement variables of the sample being examined are to be determined, for example, during tests at high temperatures. On the one hand, non-reactive substances with a chemically constant composition can, at high temperatures, not only undergo density jumps when the substance melts, but also experience a decrease in density in the molten state with increasing temperature. On the other hand, many samples, at high temperatures, are highly reactive not only towards the components of the coexisting atmosphere (e.g. oxygen), but also towards the container material surrounding the substance (e.g. ceramics, metals). When such reactions occur, it is often difficult to infer during rheological measurements whether the variations in the measurement signal are due to the rheological properties of the sample itself, to temperature changes, or to chemical changes. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is therefore to provide a method or a corresponding rheometer which achieves a solution in this regard and makes it possible to determine the density of a viscous, in particular liquid, sample, without the need to remove the sample from the rheometer and introduce it into an external density measuring device. [Means for solving the problem]

[0005] The present invention solves this problem by a method for determining the density of an at least viscous, in particular liquid, sample with the aid of a rheometer having the features of claim 1. In this method, the rheometer comprises a first measuring part for receiving the at least viscous, in particular liquid, sample and a second measuring part for immersion in the sample, the first measuring part and the second measuring part being movable relative to each other and the volume of the second measuring part being known.

[0006] Here, according to the present invention, the following steps are included: After immersing the second measuring part in the sample,The sample acts on the second measuring section measuring a normal force, the measured normal force corresponding to a buoyancy force acting between the sample and the second measurement part; Calculating the density of the sample based on Archimedes' principle using the known volume of the second measurement portion and the measured normal force.

[0007] When the second measuring part is immersed in the sample contained in the first measuring part, it is subjected to different buoyancy forces depending on the density of the viscous, in particular liquid, sample to be examined, whereby while the second measuring part is immersed in the sample, a resistance against displacement acts on the sample at the time of immersion. After the second measuring part is immersed in the sample, only the buoyancy forces in the sample act on the second measuring part. Thus, from a technical point of view, due to the buoyancy of the measuring part with a known volume of a liquid or viscous sample, the density of the sample can be measured by means of its buoyancy or determined by means of the measured normal force (Archimedes' principle on a body as stationary as possible). This advantageously allows continuous density measurements of viscous, in particular liquid, samples to be performed directly in the rheometer.

[0008] Particularly preferably, the method according to the invention can be used for determining the density of, for example, polymers, molten salts, molten metals, molten glass, lava or clinker.

[0009] In order to be able to study the temperature dependence of density, which is particularly important for rheological experiments at high temperatures, the sample can be temperature controlled during the measurement of the normal force, in particular heated and / or cooled, and the determination of the density of the sample can be repeated at different temperatures, in particular arranged to heat the sample up to a temperature of 1730°C.

[0010] In this way, it is advantageously possible to observe the melting of a sample by means of the measured normal force and, from this, to investigate in the rheometer the density jump upon melting and the decrease in density with increasing temperature in the molten state of substances that are unreactive at high temperatures and have a chemically constant composition, as well as to obtain an explanation for the behavior of samples that are highly reactive at high temperatures, in particular towards the components of the atmosphere present in the rheometer (e.g. oxygen, inert gases or forming gas) or that have temperature-dependent reactions and / or phase transitions with the measuring part materials in the sample and / or in contact with said components.

[0011] A particularly accurate determination of the density of a viscous, in particular liquid, sample to be examined can be achieved by measuring the thermal expansion of the second measuring part at various reference temperatures prior to the determination of the density. The body This can be achieved by storing the values ​​in the form of a product correction curve or volume correction table, and correcting and / or taking into account the temperature effect on the volume of the second measurement section at each measurement temperature when subsequently determining the density of the sample based on the stored values.

[0012] This procedure advantageously makes it possible to correct the influence of the thermal expansion of the measuring part on the density measurement when using a measuring part with an associated thermal expansion during rheological experiments carried out at high temperatures in a rheometer.

[0013] In order to particularly accurately determine the density of a viscous, particularly liquid, sample to be inspected, it is possible to carry out test measurements with a reference liquid having a known density at a given reference temperature at various reference temperatures before measuring the density of the sample, and to determine the temperature effect on the combination of the volume of the second measuring section and the normal force measurement, and to store this, in particular in the form of a normal force correction curve or normal force correction table, and to further be configured to correct the temperature effect on the combination of the volume of the second measuring section and the measured normal force at each measurement temperature based on the stored values ​​when subsequently determining the density of the liquid sample.

[0014] A particular advantage of this is that when calculating the density of a viscous, in particular liquid, examined sample, it is possible to combine and simultaneously take into account the volumetric variations and thermal expansion of the second measuring part as well as possibly device-specific additional effects, such as, for example, the stiffness of the rheometer and / or the expansion of the measuring axis, which occur at high temperatures.

[0015] In order to be able to determine the viscosity, in particular the density, of a liquid sample to be examined in a variety of ways, The first or second measuring part, which normally rotates in a rheological measurement, is kept stationary during the measurement of the normal force, or It is possible that the first or second measuring part is configured to rotate and / or rotationally oscillate during the measurement of the normal force.

[0016] A particular advantage of this is that, for example, it is possible to determine the density directly during a rheological oscillation test in a rheometer, or the rheological rotation test in the rheometer can be interrupted, for example, for a short time, after which the normal force is measured and the rheological rotation test is continued again, without the sample having to be removed from the first measuring part.

[0017] In rheological testing, in order to obtain directly the viscosity, in particular the exact density, of the liquid sample to be examined, in particular in the molten state at each temperature at which the test is carried out, for example without distortion due to rapid cooling or removing the sample from the rheometer, it is possible to determine the rheological parameters of the liquid sample, in particular the viscosity, in addition to determining the density of this liquid sample, in particular simultaneously with determining the density of the sample.

[0018] In order to ensure a particularly accurate determination of the viscosity, in particular the density, of a liquid tested sample, it is possible to be configured to measure the temperature of the liquid sample and / or the first measuring section and / or the second measuring section and to perform the determination of the density only when the temperature of the liquid sample and / or the first measuring section and / or the second measuring section reaches a predefined temperature threshold.

[0019] In this way it is possible particularly efficiently to avoid that thermal expansion of the second measuring part or additional device-specific effects from adversely affecting the density measurement.

[0020] In rheological tests, in particular at each temperature at which the test is carried out, in order to directly obtain the viscosity, in particular the exact density, of the liquid sample to be examined in the molten state, Before determining the density of the sample, - calculating the geometric density of at least one reference liquid from the mass of the reference liquid introduced into the first measuring part and from the position of the surface of the reference liquid determined during the approach of the second measuring part and the known shape of the first measuring part, in particular at a given reference temperature; determining the density of the reference liquid, in particular at a predefined reference temperature, according to the method according to any one of the preceding claims, and determining a correction factor by comparing the predefined value of the density of the reference liquid with a predefined value of the geometric density of the reference liquid, in particular storing it in an evaluation unit, When determining the density of the subsequent sample, it may be configured to correct the effect of the immersion depth of the second measurement part into the sample at each measurement temperature based on the determined correction coefficient.

[0021] The geometric density of at least one reference liquid is thus determined during the positioning of the second measuring part, in particular the measuring body. For this purpose, the height or position of the sample surface in the first measuring part is measured from the normal force rise on contact with the reference liquid, and the density is determined geometrically from this together with the previously measured or known mass of the sample introduced into the first measuring part and the known shape and filling height of the sample mass in the first measuring part. This initial value of the geometric density is compared according to the invention with the density value determined after immersion, and the difference between these values ​​is used as a correction value in a further method to correct the influence of the immersion depth of the second measuring part in the sample and, if applicable, the influence resulting from different proportions of the measuring shaft.

[0022] In order to avoid variations in immersion depth during the measurement of the normal force from affecting the density determined in accordance with the invention, it may be arranged that the vertical distance between both measuring parts relative to one another is kept approximately constant while measuring the normal force.

[0023] The vertical distance, or height gap, of the two measuring parts relative to one another is understood in the following to be the distance between the first measuring part 7, i.e. for example the bottom of a measuring cup, and the second measuring part 8, e.g. the tip of a measuring cylinder having a flat or pointed bottom.

[0024] It is a further object of the present invention to provide a rheometer which allows the measurement of density directly in the rheometer itself during a rheological test, without the sample having to be removed from the rheometer again and placed in a separate density measuring device in order to determine the density.

[0025] The present invention achieves this object by the following claims: 12 According to the invention, the rheometer, in particular a rotational rheometer, comprises the following components: a first measuring section for accommodating a liquid sample and a second measuring section having a known volume, the second measuring section being disposed in the rheometer so as to be immersed in the liquid sample, and the first measuring section and the second measuring section being disposed in the rheometer so as to be capable of relative motion; a normal force measuring unit arranged in the rheometer and configured in such a way that the normal force between the two measuring parts can be measured, in particular before, during and after immersion of the second measuring part in the sample, the measured normal force corresponding to the buoyancy force acting between the liquid sample and the measuring parts; and a control and processing unit for calculating the density of the liquid sample based on Archimedes' principle, in particular according to a method according to the present invention.

[0026] The invention advantageously allows the viscosity, and in particular the density, of a liquid sample to be determined directly in the rheometer by normal force measurements in the rheometer, so that the sample does not have to be removed from the rheometer for the density determination or the density determination can be performed independently of the rheological test.

[0027] A particularly useful test for viscosity, especially for liquid samples, is If the first measuring part is configured as a measuring cup having an approximately cylindrical cross section, the second measuring part is configured as a measuring body with an approximately cylindrical cross section, in particular as a rheological measuring spindle, the outer diameter of the second measuring part being smaller than the inner diameter of the first measuring part, and This can be ensured when the first and second measuring parts are arranged coaxially in the rheometer and a measuring gap having a predetermined width can be formed between the concentric walls of the first measuring part and the second measuring part.

[0028] Such a coaxial cylinder measuring system has the advantage that no lateral flow of the sample is possible, so that, for example, possible settling of particles in the sample has little influence on the measurement result.

[0029] A particularly precise temperature control of the sample in the rheometer can be achieved if the rheometer is equipped with a heating and / or cooling device for temperature control. In this way, for samples that are highly reactive at high temperatures, it is possible to check whether fluctuations in the measurement signal are due to rheological processes, temperature fluctuations or chemical changes.

[0030] This not only allows for an additional measurement variable at high temperatures to be obtained by direct in situ density measurement, but also allows for simultaneous consideration and comparison with temperature and rheological measurement variables by continuous measurement. In this way, it is possible to inversely deduce the relationship between chemical changes due to reactions with the material of the measurement area or within the sample and the resulting density changes.

[0031] The configuration of the rheometer according to the invention allows for targeted induction of density changes, in addition to easily correcting for undesired effects, or density changes can be part of high-temperature processes or experiments. Examples of technically relevant density changes are oxidation-reduction processes in redox-sensitive solutions, e.g. separating native metals (suspensions) or molten metals (emulsions) from clinker in metal extraction, corrosion of refractory materials in the same, thermal degradation of glasses or ionic liquids, and alloy changes due to evaporation or dissolution in the metallic materials of the measuring part.

[0032] The rheometer according to the present invention comprises a heating and / or cooling device: in the first measuring part, in particular in the form of at least one Peltier element, and / or In particular, it is formed as a temperature-controlled cover that can be placed over both measuring parts, and / or The measuring section and the sample are temperature-controlled by gas or liquid, and / or the measuring section and the sample are formed as a convection heating chamber and / or a convection cooling chamber. If the first and second measuring parts are designed as an arranged high-temperature furnace, it is possible to have a very compact construction.

[0033] According to one advantageous variant of the rheometer according to the invention, the rheometer comprises: at least one measuring motor having a measuring shaft, the first measuring part or the second measuring part being connected to the measuring shaft, each measuring part being capable of a relative rotational and / or vibrational movement with respect to the other measuring part, The control and processing unit is configured to define the rotation speed of the measurement motor and to measure the torque occurring on the measurement shaft and / or is configured to define the torque of the measurement motor and to measure the rotation speed of the measurement motor.

[0034] According to a further advantageous variant of the rheometer according to the invention, The rheometer is a first measuring motor having a first measuring shaft, a first measuring part being connected to the first measuring shaft, the first measuring part being capable of performing a rotational and / or oscillatory movement, a second measuring motor having a second measuring shaft, the second measuring part being connected to the second measuring shaft, the second measuring part being capable of performing a rotational and / or oscillatory movement independently of the first measuring part, The control and processing unit comprises: in each case, the rotational speed of the first and / or second measuring motor is determined in order to measure the torque acting on the first and / or second measuring shaft; and / or In both cases, it is arranged to define a torque of the first measurement motor and / or the second measurement motor and to measure the rotation speed of the first measurement motor and / or the second measurement motor.

[0035] An advantageous variant of the rheometer according to the invention, which allows experiments at different temperatures to be carried out with particularly little effort, can be provided if the control and processing unit is arranged to control a heating and / or cooling device.

[0036] If the control and processing unit comprises a memory device and is configured, in particular according to a method of the present invention, to store the previously determined volume correction curve and / or volume correction table and / or normal force correction curve and / or normal force correction table in the memory device, a particularly accurate density determination is ensured by simultaneously and particularly easily taking into account additional device-specific effects which may possibly occur in the event of volumetric changes or thermal expansion of the second measuring part and / or temperature changes.

[0037] An advantageous embodiment of the rheometer according to the invention, which allows rheological experiments to be evaluated particularly accurately and with particularly little effort, can be provided if the control and processing unit is configured to evaluate the measured values ​​determined for each measuring shaft and / or each measuring motor, in particular simultaneously with determining the density of the liquid sample and to determine at least one rheological parameter of the liquid sample, in particular the viscosity.

[0038] According to one advantageous variant of the rheometer according to the invention, a normal force measuring unit is connected to the first measuring part and a further normal force measuring unit is connected to the second measuring part, which further normal force measuring unit can be configured, preferably simultaneously with the normal force measuring unit, to measure the normal force between both measuring parts, in particular before, during and after immersion of the second measuring part in the sample.

[0039] Further advantages and configurations of the invention will become apparent from the description and the accompanying drawings.

[0040] Exemplary embodiments of the invention are illustrated diagrammatically in the drawings and will hereinafter be described, by way of example, with reference to the drawings. [Brief description of the drawings]

[0041] [Figure 1] FIG. 1 shows a first embodiment of a rheometer according to the present invention. [Diagram 2] FIG. 2 shows a second embodiment of a rheometer according to the present invention. [Diagram 3] FIG. 4 shows a third embodiment of a rheometer according to the present invention. [Figure 4] FIG. 1 shows the relationship between sample density and measured rheometer normal force for various test section diameters. [Diagram 5] FIG. 1 compares the density of various samples determined according to the present invention with a reference value for each sample. [Figure 6]FIG. 1 shows the precision obtained for the density of samples measured according to the invention by rheometers with various measuring section diameters for different sample densities. [Figure 7] FIG. 1 shows the precision obtained for the density of samples measured according to the invention by rheometers with various measuring section diameters for different sample densities. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] In the present invention, Various A rheometer 100 can be used or adapted for use. The rheometer 100 according to the invention can be, for example, a rotational rheometer. The rheometer 100 has a configuration or components known from the prior art. The rheometer 100 comprises, for example, a base 1, a spindle 2, a rheometer housing 3, a measuring motor 4 and a measuring shaft 14. The spindle 2 in combination with the spindle motor 11 can be adjusted in height in a defined manner, besides which automated solutions are also known, with which the distance between the two measuring parts 7 and 8 can be varied. In the rheometer housing 3, a control and processing unit is usually installed. Such a rheometer 100 according to the invention can furthermore be The sample 12 acts on the second measuring section 8 Normal force F N The device further includes at least one normal force measuring unit 5 for determining

[0043] A rotational rheometer typically has two interchangeably arranged measuring parts on the measuring shaft, namely a first measuring part 7, e.g. a measuring cup for receiving a viscous, in particular liquid, sample 12 to be examined, and a second measuring part 8, e.g. a measuring cylinder or measuring tube which is immersed in the sample 12 during the measurement.

[0044] The sample 12 to be examined is introduced into the measurement space of the rotational rheometer between the first measuring part 7 and the second measuring part 8. During the measurement, the sample 12 is sheared between the rotating or oscillating part and the stationary part of the setup. The first measuring part 7 and the second measuring part 8 are offset relative to each other around a common axis of rotation in a rotational movement, and the sample is subjected to a shear load by the twisting of the measuring parts 7 and 8 relative to each other. In this case, not only rotational movements but also rotational-oscillating movements are possible.

[0045] The geometry of the measurement setup and the rotational speed and / or number of rotations of each moving measuring part result in a shear rate. The torque that the sample exerts against this movement is measured and, on this basis, the shear stress, viscosity and other rheological parameters can then be measured.

[0046] The measuring parts 7 and 8 can basically have different geometries in the rheometer 100. This can be, for example, a plate / plate measuring system, a concentric cylinder measuring system, a cone / plate measuring system or configurations specific to different application areas, for example the measurement of immobilization reactions of dispersions or components or electrorheological measurements. Here, the first measuring part 7 can be stationary and the second measuring part 8 can rotate during the rheological measurements (Searle system) or vice versa (Couette system).

[0047] When the second measuring part 8, e.g. a simple measuring cylinder, is immersed in the sample contained in the first measuring part 7, e.g. a measuring cup, the second measuring part 8 experiences a buoyancy force F which varies depending on the density of the sample. A Receive.

[0048] The normal force or first normal force rise which initially acts on the second measuring part 8 upon immersion corresponds to the resistance of the sample 12 against displacement upon immersion. The first normal force rise when the second measuring part 8 impacts the sample surface can therefore be used, for example, to determine the height of the sample.

[0049] The rheometer 100 itself has a high rigidity on the base 1, since the gap height has to be kept constant and the immersed second measuring part 8 has to be stationary and not, for example, twisted. The weight of the second measuring part 8 is recorded by the measuring motor 4 on the base 1. The resulting normal force F N is the buoyancy or lift force F acting between the sample 12 and the measuring parts 7 and 8. A That is, the buoyancy force F acting on the second measuring part 8 by displacing the sample 12 according to Archimedes' principle without applying any additional displacing resistance is equivalent to A acts in conjunction with a fixed or constant measuring gap 13 and a constant height adjustment of the second measuring part 8 in the first measuring part 7, which is, for example, a measuring cup, after immersion of the second measuring part 8 in the sample 12, i.e. when the second measuring part 8 is in a stationary state.

[0050] By measuring gap 13 in a concentric measuring system is understood the distance between the approximately cylindrical flat surfaces of measuring parts 7 and 8 which rotate relative to one another. The height gap, i.e. the vertical distance or minimum distance, between the first measuring part 7, i.e. the bottom of a measuring cup, and the second measuring part 8, e.g. the tip of a measuring cylinder with a flat or pointed bottom, is kept constant in the rheometer 100, which is required to have a high stiffness due to the bearings of the base 1 and the measuring shaft used.

[0051] Using this condition, it is possible to determine the density ρ of the sample 12 according to Archimedes' principle by measuring the normal force in the rheometer 100. Here, the density ρ of the sample 12 is expressed by the following relational expression or equation: m=F N / g (1) ρ=m / V (2) ρ=F N / (V * g) (3) Here, m is the mass of sample 12, F N is the measured normal force of the sample 12 , g is the gravitational acceleration, ρ is the density of the sample 12 , and V is the volume of the second measurement portion 8 .

[0052] This means that, according to the present invention, the rheological parameters of sample 12, such as the viscosity and density p of sample 12, can be measured in situ and almost simultaneously in rheometer 100.

[0053] Normal force F N Measuring can be achieved in a variety of ways in the rheometer 100 according to the present invention. The sample 12 acts on the second measuring section 8 Normal force F N The exact method of measuring is not important here.

[0054] For example, as described in US 2006 / 081037 A1, a normal force measuring unit 5 can be provided for determining normal forces and / or torques occurring on the measurement shaft 14 during measurements. The normal force measuring unit 5 comprises a first holding part connected to the measurement shaft 14 and a second holding part fixedly fixed to the base. The second holding part is connected to the first holding part via spring-like connections, at least one of the connections being fitted with a strain gauge capable of determining the deformation of the connection.

[0055] The normal force measuring unit 5 comprises an encoder disk extending approximately perpendicular to the longitudinal axis of the measuring shaft 14, as in DE 10310676 A1, measures the axial movement of the encoder disk oriented in the direction of the longitudinal axis of the measuring shaft 14, and from the measured movement of the encoder disk, determines the normal force F of the measuring shaft 14. N It is possible to obtain

[0056] The normal force measuring unit 5 may also have a circular pressure sensor, as in DE 19632589 A1, which is arranged in the center of the first measuring part 7 or of the lower measuring plate at right angles to the axis of the measuring part, the measurement signal of which, for example an electrical signal, corresponds to the normal force F generated in the viscoelastic sample 12 by shear in the measuring gap 13. N is clearly associated with

[0057] Furthermore, the first measuring unit 7 and / or the second measuring unit 8 may be provided with a plurality of normal force sensors, or a distance sensor may be provided to measure the change in the axial distance of the spring 7 connected to the second measuring unit 8. This allows the normal force F N can be calculated.

[0058] Also, the normal force measuring unit 5 may be housed in its own housing separate from both measuring sections 7 and 8 .

[0059] When carrying out the rheological vibration test, the density ρ of the sample 12 can be determined directly according to the invention, and when carrying out the rotation test, the normal force F N It is sufficient to briefly interrupt the rheological measurement to measure the density ρ of the sample 12. That is, the density ρ of the sample 12 can be measured directly in the first measuring part 7 with a short interruption of the rheological measurement or directly during the rheological measurement. In this case, it is not important which of the measuring parts 7 and 8 is actually in motion and which of the two measuring parts 7 and 8 is stationary when measuring the rheological properties. What is important is simply that the measuring parts 7 and 8 move relative to each other.

[0060] The different principles of the rheometer 100 according to the invention or of the method according to the invention for measuring the density ρ of at least a viscous, in particular liquid, sample 12 by means of the rheometer 100 can therefore also be applied for the measuring motor. On the one hand, for example, the rotation speed of the motor can be defined and the resulting torque can be measured. Or, conversely, the torque of the motor can be defined and the resulting rotation speed can be measured. Here, the rotation speed can be measured, for example, by means of an angle encoder and the torque can be determined from the power consumption. The principle of two separated motors simply comprises a rotating motor and a torque measurement.

[0061] If the temperature of the sample 12 is controlled, the density ρ of the sample 12 and the rheological properties of the sample 12 can also be determined as temperature dependent parameters.

[0062] This temperature control can be performed in various ways. For example, the first measuring part 7 may be configured as a heatable measuring cup, as described in US 6240770 B1 or DE 19911441 A1. The rheometer 100 according to the invention may also comprise a temperature-controlled cover, as described in US 6571610 B1 or AT 409422 B, or may comprise a high-temperature oven for carrying out rheological tests. Convection heating and / or cooling chambers are also known, in which the measuring parts 7 and 8 as well as the sample 12 are temperature-controlled by gas or liquid. Such systems are described, for example, in AT 513661 B1.

[0063] For density measurements, the second measuring part 8 may have any configuration and the weight of the second measuring part 8 does not play any role since the second measuring part 8 is fixed or held vertically.

[0064] The known volume V of the second measuring part 8 is important for the present invention. For the determination of the density ρ of the sample 12 according to the present invention, the volume V of the second measuring part 8 is temperature-dependent, known or predefined and is for example stored in the control and processing unit. Thus, it is possible to read out the known volume V of the second measuring part 8 at any time and to determine the density ρ of the sample 12, for example during a rheological test of the sample 12.

[0065] Depending on the density ρ of the sample 12 to be determined, the following applies: the lighter the sample 12 (the smaller the density ρ), the more difficult the measurement is, since the discernible buoyancy F A As is clear from the above formulas (1) to (3), if not only the sample density ρ is high but also the displaced volume V (volume V of the second measurement portion 8) is large, the normal force signal F NIn other words, the measurable sample density or measurement accuracy can be controlled by selecting the second measurement unit 8.

[0066] It is therefore possible to provide a measuring body or second measuring part 8 with a precisely measured volume V for the various density regions. The dimensions of the first measuring part 7 and the second measuring part 8 are determined for each sample 12 in such a way that the normal force F N So that a good measurement signal of the buoyancy force F A can be chosen such that the change in is sufficiently large.

[0067] Alternatively, it applies that the smaller the density ρ of the sample 12 or liquid to be examined, the larger the second measuring portion 8 that needs to be used.

[0068] From equation (3), the flotation or buoyancy force F A , or a signal of the normal force to be measured is obtained. F N =ρ * (V * g) Therefore, in order to produce comparable measurement values ​​or to lead to comparable normal force differences in the event of relative density changes, the volume V of the second measuring part 8 or measuring body must be larger the smaller the density ρ.

[0069] That is, the practically usable dimensions of the second measuring part 8 or measuring body are determined by the separation force of the normal force and the sample to be inspected. For example, the minimum measurable normal force is 5 * 10 -5 N (50 μN). At the same time, optionally, the measurement gap 13 between the measuring parts 7 and 8 must be large enough to avoid boundary effects. Again, each option is influenced by the viscosity and surface tension of the sample 12.

[0070] It is also possible to carry out a more accurate calibration at the start of the measurement. Here, for example, after the sample 12 has melted, the immersion process of the second measuring part 8 and the position of the sample surface can be observed by the rise in the normal force signal. The exact volume of the melted sample 12 in the first measuring part 7 is thereby determined from the geometrical data of the first measuring part 7 and the position of the sample surface. Since the initial weight is known, the geometrical density ρ of the sample 12 can be calculated by the above-mentioned equation (2). geo It is possible to determine:

[0071] By comparison with the density ρ of the second measuring part 8 after immersion determined according to the invention, it is possible to obtain accurate knowledge of the exact immersion depth and of the volume displaced by the second measuring part 8 and the measuring shaft, and the buoyancy force F caused by the displacement of the sample 12 by the measuring shaft and the second measuring part 8. A It is possible to take into account

[0072] In this way, two methods of (melt) density determination are available within the measurement process: one based on the above-mentioned equations (1) to (3) and the measured normal force F N and the volume V of the second measuring part 8, which is known, and the other is a method in which a first normal force increase during immersion of the second measuring part 8 in the sample 12, which corresponds to the position of the sample surface when the measuring parts 7 and 8 are brought together, is used to determine the volume of the sample 12 and the density ρ of the sample 12 can be calculated via the mass m of the sample 12, which is determined for example by weighing the sample 12 before it is introduced into the second measuring part 8 or by measuring the normal force in the first measuring part 7 and determining the mass in situ according to equation (1). That is to say, the mass of the sample 12 can alternatively be determined when it is introduced into the first measuring part 7, for example by determining the normal force change.

[0073] By comparing the two types of density determination methods, it is possible to improve the accuracy or to validate the density values ​​determined by the Archimedes measurement method. Optionally, the correction values ​​determined for the immersion depth or the proportion of the measuring shaft are utilized for a subsequent measurement of the density ρ, for example during the execution of a temperature profile.

[0074] 1 shows a first embodiment of a rheometer 100 according to the invention, where the rheometer 100 is a rotational rheometer. The rheometer 100 comprises a base 1, a height-adjustable spindle 2 driven by a spindle motor 11, a rheometer housing 3 containing a control and processing unit, and a measurement motor 4 arranged on the base 1 and also housed in the rheometer housing 3.

[0075] A control and processing unit is connected to all measuring units or sensors in Fig. 1 and evaluates the obtained measurement data, but is not shown separately in Figs. 1 to 3, because it can be integrated at various positions in the rheometer 100 or is a unit separate from the rheometer 100 and connected by wire or wirelessly to the components of the rheometer in order to control these components or to receive data. The control and processing unit can be accommodated, for example, in the rheometer housing 3. The control and processing unit not only controls the measuring motor 4, but also calculates or receives the measured values ​​measured in relation to the measuring shaft 14 and evaluates these measured values ​​in order to derive or determine the rheological parameters.

[0076] The Rheometer 100 also: The sample 12 acts on the second measuring section 8 Normal force F NThe control and processing unit is connected to the normal force measuring unit 5 and is capable of carrying out the method according to the invention for determining the density of the sample 12. The normal force measuring unit 5 comprises a memory device, in which the known volume of the second measuring part 8 and possibly calibration data and volume correction curves and / or volume correction tables and / or normal force correction curves and / or normal force correction tables can be stored, on the basis of which the determined density ρ of the sample 12 can be corrected. Furthermore, the geometric density ρ geo In order to determine the above, geometric data of the first measurement unit 7 may be stored.

[0077] At an exchange fixture 6, the so-called tool master, the second measuring part 8 can be exchanged and the data characterizing the measuring body of the second measuring part 8 can now be transmitted contactlessly. This is particularly preferred for adapting the second measuring part 8 to the density ρ of the sample 12 or for forming the second measuring part 8 from different materials suitable for the temperatures reached during the test.

[0078] In a first embodiment, the measuring parts 7 and 8 are concentrically arranged measuring cylinders. In the first measuring part 7 outside the hollow cylinder, which is the measuring cup, a second measuring part 8 is arranged, which is a coaxial closed cylindrical measuring body with the same axis of rotation. The sample 12 to be measured is placed in the measuring gap 13 between the measuring parts 7 and 8. The measuring parts 7 and 8 are arranged at a defined distance from each other, so that the gap width and gap height are defined.

[0079] Alternatively, in all embodiments of the rheometer 100 according to the present invention, the first measuring part 7 and the second measuring part 8 may have additional structures on their cylindrical outer surface to prevent wall slip effects during the measurement.

[0080] In the first embodiment, the second measurement unit 8is connected to the measuring shaft 14, which is driven by the measuring motor 4. To this end, the second measuring part 8 undergoes a rotational and / or oscillatory movement relative to the first measuring part 7, whereas the first measuring part 7 remains stationary. In this case, the control and processing unit, for example, defines the number of revolutions of the measuring motor 4 and measures the torque occurring on the measuring shaft 14 and / or defines the torque of the measuring motor 4 and measures the number of revolutions of the measuring motor 4. The control and processing unit then evaluates the measured values ​​determined for the measuring shaft 14 and / or for the measuring motor 4, for example simultaneously with the determination of the density ρ of the liquid sample 12, and on the basis of this determines the rheological parameters of the sample 12, for example the viscosity, according to methods known from the prior art.

[0081] Coaxial cylinder measuring systems have the advantage that no lateral flow of the sample is possible, so that possible settling of particles in the sample, for example, has little influence on the measurement result.

[0082] For the cylinder measuring system it is advantageous to use materials whose thermal expansion coefficient in the temperature range to be examined is as low as possible or is very accurately known, for example certain glass ceramics / metal alloys or platinum (platinum alloys).

[0083] In measurements where no reaction is checked, it is furthermore advantageous to use for the cylinder measuring system, or generally for the first measuring part 7 and the second measuring part 8, materials which are unreactive or barely reactive towards the sample material, such as many precious metal alloys.

[0084] In the first embodiment, the temperature control of the sample 12 takes place via the first measuring part 7 and the second measuring part 8. In this cylinder measuring system, the measuring cup and the measuring body are temperature controlled by Peltier elements. Here, a double measuring cup is used, so that a temperature homogenization can be realized. In this way, it is possible to suppress the temperature gradient occurring in the sample 12 in the measuring gap 13 or shear gap between the inner wall of the measuring cup and the outer wall of the measuring cylinder. The measuring cups in this case consist of a material with good thermal conductivity. Here, a separating gap separates the inner measuring cup from the outer isothermal cup surrounding it.

[0085] The normal force measurement is carried out in a first embodiment in an air bearing, as described in AT 404192 B and US 6167752 B1. The rheometer 100 comprises a measurement motor 4 which drives a measuring shaft 14. The measuring shaft 14 carries a disk mounted in an air bearing of a stator. The normal force measuring unit 5 of the rheometer 100 further comprises at least one path sensor, which determines the axial movement of the measuring shaft 14 on the basis of the viscoelastic properties of the sample 12 to be examined. For the normal force measurement, the path sensor is arranged on the stator in the region of the air bearing and records the movement of the disk relative to the stator, which takes place in the axial direction of the measuring shaft 14.

[0086] As clearly shown in Fig. 1, the rheometer 100 comprises a first temperature measuring unit 10 arranged in a first measuring part 7, which is a measuring cup, and a second temperature measuring unit 9 arranged in a second measuring part 8, which is a measuring cylinder. By means of these temperature measuring units 9 and 10 it is possible to determine whether the temperature of the sample 12 has reached a predefined temperature when the measuring gap 13 no longer changes due to temperature fluctuations. In order to check whether the measuring gap 13 still changes, a non-contact distance sensor may be provided below the first measuring part 7, which is a measuring cup, to check the fluctuations.

[0087] 2 shows a second embodiment of a rheometer 100 according to the invention, which has a similar configuration to the first embodiment. However, unlike the first embodiment, in the second embodiment the first measuring part 7 or measuring cup is not kept stationary but performs a rotational movement. The second measuring part 8 is connected to a measuring shaft 14, and the control and processing unit determines the number of revolutions of the measuring motor 4 to measure the torque occurring on the measuring shaft 14.

[0088] In the two exchange fixtures 6, it is possible to exchange both measuring parts 7 and 8, and the data characterizing the measuring body can now be transmitted contactlessly. This is not only to allow the second measuring part 8 to be adjusted according to the density ρ of the sample 12 or to be constructed of different materials adapted to the temperatures reached during the test, but also to allow the volume of the sample 12 accommodated in the first measuring part 7 to be adjusted according to the buoyancy F of the sample 12. A or the density ρ of the sample 12.

[0089] 3 shows a third embodiment of a rheometer 100 according to the invention, which has a similar configuration to the first and second embodiments, however, in the third embodiment the rheometer 100 comprises two measurement motors 4 and 4′.

[0090] The first measuring motor 4 is arranged in the first housing 3 and comprises a first measuring shaft 14 to which the first measuring part 7 is connected. The first measuring shaft 14 thus causes the first measuring part 7 to undergo a rotating and / or oscillating movement. The second measuring motor 4' is arranged in the second housing 3' and comprises a second measuring shaft 14' to which the second measuring part 8 is connected. The second measuring shaft 14' thus causes the second measuring part 8 to undergo a rotating and / or oscillating movement independently of the first measuring part 7.

[0091] The control and processing unit determines the respective rotation speeds of the first measuring motor 4 and the second measuring motor 4' and measures the torque occurring on the first measuring shaft 14 and the second measuring shaft 14' or determines the torque of the first measuring motor 4 and the second measuring motor 4' and measures the rotation speeds of the first measuring motor 4 and the second measuring motor 4'.

[0092] The normal force measuring unit 5 is accommodated in the third embodiment in the first housing 3. In the two exchange fixtures 6, it is possible to exchange both measuring parts 7 and 8, as in the second embodiment, and data characterizing the measuring body or the second measuring part 8 can now be transmitted contactlessly.

[0093] However, in the rheometer 100 shown in the third embodiment, it is also possible to preferably arrange the normal force measuring unit 5 in the first housing 3 or in the second housing 3', or possibly in both housings 3 and 3'. This allows the normal force F N can be measured not only from above but also from below, or possibly from both.

[0094] [Density measurement example] In the following figures 4 to 7 the results of a series of test measurements for determining density by the method according to the invention are summarized, which were carried out on different viscous or liquid samples 12 or on rheometers 100 with different measuring system diameters, i.e. the second measuring part 8, which is immersed in the sample 12, has different diameters DM or outer diameters.

[0095] 4, 6 and 7, the measured normal forces F, respectively, indicated in [N], of the rheometer 100 with various measurement system diameters. N and [kg / m 34 to 7, CC stands for concentric cylinder, i.e., the rheometer 100 in which the first measuring part 7 and the second measuring part 8 are formed as a cylindrical measuring cup and measuring cylinder arranged concentrically. The alphabet combination PT stands for platinum material or platinum-rhodium alloy, and DM stands for the diameter of the second measuring part 8 and reflects the alphabet. Here, the exact gap width 13 is determined by the normal force F N The measuring diameter DM of the second measuring section 8, which corresponds to the symbol of the rheometer in FIG. 4, is given in [mm] and is also shown in FIGS.

[0096] As shown in Figure 4, the measured normal force F N increases as the density ρ of the sample 12 increases. N It turns out that the relationship between the density ρ of the examined sample 12 and the measurement system diameter DM is independent for all rheometers 100. Here, a given density, e.g. 2000 kg / m 3 The normal force F measured for sample 12 having N increases with each diameter DM of the measuring system (imagined horizontal line). That is, the normal force F N is smaller when the measurement system diameter is small (e.g., rheometers CC11, PtCC14) than when the measurement system diameter is large (e.g., rheometers CC27, CC27.6).

[0097] The accuracy of each rheometer 100 or related measurement system was calculated using each data. When the second measurement part 8 is small, the buoyancy acting on it is smaller than when the second measurement part 8 is large. Therefore, the normal force F N The difference in density ρ of sample 12 is also extremely small. N6 and 7 for various sample densities ρ. However, in any rheometer 100 or any measurement system, the density ρ of the sample 12 is proportional to the normal force F measured for the reactions and temperature variations described above. N Therefore, it is possible to measure with sufficient accuracy.

[0098] Additionally, it was determined how much density difference (percentage) the rheometer 100 can discern from a cylinder of given dimensions. To this end, the measured normal force F available in the rheometer 100 was N and density ρ.

[0099] In Figures 6 and 7, the horizontal axis indicates the diameter DM of the second measuring part 8, and the vertical axis indicates the accuracy (relative accuracy) ACC of the density for different measured body diameters. rel where p is expressed as a percentage. The values ​​are taken from the solution for the normal force of the rheometer 100 for the specified density values. If the initial density of the diameter DM of the second measuring section 8 is chosen large enough, the detectable change in density ρ is in the sub-percentage range (e.g. CC27.6). For high temperature measurements, this solution has a density of 114 kg / m 3 , and in the MCR measurement, the value for CC28 is 19 kg / m 3 and 7kg / m for CC39. 3 It is.

[0100] In Fig. 5, various inspected samples 12 are compared with the density reference value ρ ref The horizontal axis shows the density reference value ρ of the inspected sample 12. ref is [kg / m 3 ], while on the vertical axis is plotted the normal force F N and the value of density ρ of the sample 12 calculated from the known volume V of the second measurement section 8 is [kg / m 3] are plotted. Various liquids were tested. Sample numbers N26 and AK1000 are silicone oil, H2O is water, and H2O+10 wt% NaCl and H2O+20 wt% NaCl are saline solutions. All samples were tested in the temperature range of -20°C to 140°C. This temperature is not directly indicated in FIG. 5, but in FIG. 5 the highest density ρ calculated for each component corresponds to the lowest measured temperature, while the lowest density ρ is calculated at the highest measured temperature. In the tests summarized in Fig. 5, two different measuring systems were used, indicated in Fig. 5 by CC28 (with a diameter DM of the second measuring part 8 of 28 mm) and CC39 (with a diameter DM of the second measuring part 8 of 39 mm). These measuring systems were chosen in order to compensate for the lower density ρ of the examined sample 12 via the larger volume V of the second measuring part 8 or measuring cylinder, and thus to obtain a sufficiently large normal force F N With these measuring systems or measuring diameters DM it is advantageously possible to determine the density ρ of the sample 12 particularly accurately, which is lower than the density of, for example, a very high silicate melt.

[0101] In contrast, for silicate melts with a very high density ρ, it is possible to use a second measuring part 8 which itself has a small diameter DM, as shown in Figures 6 and 7 (see, for example, CC11, PtCC14, etc.).

[0102] Here, each test was carried out according to the following steps according to the present invention. 1) Measure the initial weight and determine the sample volume. 2) The sample 12 is placed in the first measuring part 7 and the measuring part 7 is attached to the rheometer 100, or vice versa. 3) The second measurement unit 8 is immersed in the sample 12. 4) In some cases, the temperature of the first measurement part 7 is controlled by the first measurement part 7 or a measuring cup whose temperature is controlled by, for example, a Peltier element, and the sample 12 and the second measurement part 8 are kept in thermal equilibrium until they reach thermal equilibrium. 5) After the second measurement part 8 is immersed in the sample 12, the normal force F N Measure. 6) Based on equation (3), the measured normal force F N And the density ρ of the sample 12 is calculated using the known volume of the second measurement portion 8.

[0103] As mentioned above, in order to enable a particularly accurate density determination, it is optionally possible after step 3) to determine the state of the sample surface during the immersion step of the second measuring part 8 and to determine the geometric density ρ geo In this case, it is also possible to calculate the normal force F N Following the measurement of the normal force F during the immersion process or immediately after the start of the immersion process, N Calculate the deviation from the initial value of this normal force F N It is also possible to calculate density fluctuations from the fluctuations in

[0104] Normal force F N is in the range of 0.2-0.3 N for the CC28 measurement system and is approximately a factor of 3 higher, in the range of 0.7-0.8 N for the CC39 measurement system.

[0105] The measurements (30 measurements taken over 3 minutes, averaged) were compared with the known density reference values ​​ρ for the above components according to equations (1) to (3) above. ref The results are shown in Figure 5.

[0106] The resulting normal force F after complete immersion of all liquids N As expected, samples 12 that have a very high viscosity or are highly elastic are difficult to measure the density of.

[0107] The components used have viscosities between <1 mPas and 100 Pas in the temperature range examined, which meaningfully represents the viscosity range of silicate (glass) melts, salt solutions, and molten metals.

[0108] The results in Fig. 5 show that, although a certain temperature drift occurs for all samples 12 because the thermal expansion of the second measuring part 8 or the measuring body was not taken into account, there is a systematic agreement between the reference values ​​and the measured values. This means that, even without taking into account the thermal expansion of the second measuring part 8, the density ρ of each inspected sample 12 can be determined sufficiently accurately by the method according to the invention.

[0109] As mentioned above, in advance, i.e. before the test for determining the density ρ of the sample 12, the thermal expansion of the second measuring part 8 for various reference temperatures is measured. The body If the density ρ of the sample 12 is then determined in the form of a product correction curve or a volume correction table, the accuracy of the calculated density ρ can be increased. When the density ρ of the sample 12 is then determined, the effect of temperature on the volume V of the second measuring portion 8 at the respective measuring temperature is known and this effect can be corrected or taken into account in the density calculation on the basis of the stored values.

[0110] Optionally, prior to the test for determining the density ρ of the sample 12, it is possible to determine not only the influence of the temperature on the volume V of the second measuring part 8, but also on the normal force measurement at various reference temperatures by carrying out measurements of the density ρ of a reference liquid, the density ρ of which is known at a given reference temperature. The volume V of the second measuring part 8 and the influence of the temperature on the normal force measurement are in this case stored in the control and processing unit, for example in combination with a normal force correction curve or a normal force correction table, and this influence can be corrected or taken into account during the density measurement on the basis of the stored values.

[0111] As further evidenced in FIG. 5, furthermore, the measurements or density values ​​are quite consistent, with the standard deviation over the 30 measurements being shown with error bars that are much smaller than the symbol size used.

[0112] Silicone oils do not evaporate in the temperature range used and have a relatively low surface tension (0.02 N / m), which makes them somewhat easier or more accurate to measure (maximum deviation of 5%, often only 1%).

[0113] The aqueous samples, as expected, show a somewhat larger dispersion near the boiling point, since here the evaporation of the samples begins and fluctuates somewhat more strongly (maximum 5-10% deviation) due to the significantly higher surface tension (0.06 N / m) than for silicone oil. However, the method according to the invention allows sufficiently accurate density measurements for all samples 12.

Claims

1. A method for determining the density (ρ) of an at least viscous sample (12) with a rheometer (100), said rheometer (100) comprising a first measuring part (7) for receiving said at least viscous sample (12) and a second measuring part (8) immersed in said sample (12), said first measuring part (7) and said second measuring part (8) being movable relative to each other, said second measuring part (8) having a volume (V) known, After the second measurement part (8) is immersed in the sample (12), a normal force (F) acting on the second measurement part (8) by the sample (12) is measured. Ｎ ), the measured normal force (F Ｎ ) is the buoyancy force (F) acting on the second measurement part (8) due to the sample (12). Ａ ) and The density (ρ) of the sample (12) is calculated based on Archimedes' principle by the known volume (V) of the second measuring portion (8) and the measured normal force (F Ｎ ) and calculating the Prior to determining the density (ρ), the thermal expansion of the second measuring part (8) at various reference temperatures is stored in the form of a volumetric correction curve or volumetric correction table, 4. A method according to claim 3, characterized in that the temperature effect on the volume (V) of the second measuring portion (8) is corrected and / or taken into account at each measuring temperature based on the stored value when determining the density (ρ) of the sample (12) thereafter.

2. The method according to claim 1, characterized in that the at least viscous sample (12) is liquid.

3. The sample (12) is subjected to the normal force (F Ｎ 3. The method according to claim 1 or 2, characterized in that the sample (12) is heated and / or cooled during the measurement of density (ρ) and the determination of density (ρ) is repeated at different temperatures.

4. Before measuring the density (ρ) of the sample (12), test measurements are carried out at various reference temperatures using a reference liquid whose density (ρ) at a given reference temperature is known, and the temperature effect on the combination of the volume (V) and normal force measurement of the second measuring section (8) is stored in the form of a volume correction curve or volume correction table; During the subsequent determination of the density (ρ) of the sample (12), the volume (V) of the second measurement portion (8) at each measurement temperature and the measured normal force (F Ｎ 4. The method according to claim 1, further comprising correcting the temperature effect on the combination of the two components based on the stored values.

5. Before determining the density (ρ) of the sample (12), The geometric density (ρ ｇｅｏ ) from the mass of the reference liquid introduced into the first measurement unit (7), the position of the surface of the reference liquid determined when the second measurement unit (8) is brought closer, and the known shape of the first measurement unit (7) at a predetermined reference temperature; The density (ρ) of the reference liquid at the predetermined reference temperature is determined according to a method according to any one of the preceding claims, and the predetermined value of the density (ρ) of the reference liquid is calculated based on the geometric density (ρ) of the reference liquid. ｇｅｏ ) determining a correction factor by comparing it with a predetermined value of the correction factor and storing it in the evaluation unit, 5. The method according to claim 1, further comprising: correcting the influence of the immersion depth of the second measuring portion (8) into the sample (12) at each measuring temperature when determining the density (ρ) of the sample (12) thereafter based on the determined correction factor.

6. The first measuring unit (7) or the second measuring unit (8) measures the normal force (F Ｎ ) is kept stationary during the measurement, or The first measuring unit (7) or the second measuring unit (8) measures the normal force (F Ｎ 6. The method according to claim 1, wherein the measuring device is rotated and / or rotated oscillated during the measurement of the distance .

7. 7. The method according to claim 1, further comprising, in addition to determining the density (ρ) of the sample (12), determining rheological parameters of the sample (12) at the same time as determining the density (ρ) of the sample (12).

8. The method of claim 7, wherein the rheological parameter is viscosity.

9. 9. The method according to claim 1, further comprising measuring the temperature of the sample (12) and / or the first measuring section (7) and / or the second measuring section (8) and determining the density (ρ) only when the temperature of the sample (12) and / or the first measuring section (7) and / or the second measuring section (8) reaches a predefined temperature threshold.

10. The normal force (F Ｎ 10. The method according to claim 1, wherein the vertical distance of both measuring parts (7, 8) relative to one another is kept approximately constant during the measurement of the measuring points (7, 8).

11. A rheometer (100) for determining the density (ρ) of at least a viscous sample (12), comprising: a first measuring section (7) for accommodating the sample (12) and a second measuring section (8) having a known volume (V), the second measuring section (8) being arranged in the rheometer (100) so as to be immersed in the sample (12), and the first measuring section (7) and the second measuring section (8) being arranged in the rheometer (100) so as to be capable of relative movement; A normal force (F) acting on the second measurement part (8) by the sample (12) before, during, and after immersion of the second measurement part (8) in the sample (12) is Ｎ A normal force measuring unit (5) arranged in the rheometer (100) and configured to measure the normal force (F Ｎ ) is the buoyancy force (F) acting between the sample (12) and the second measurement part (8). Ａ ) a normal force measuring unit (5), a control and processing unit for calculating the density (ρ) of the sample (12) based on Archimedes' principle, the rheometer (100) includes a heating and / or cooling device for temperature control of the viscous sample (12); The heating and / or cooling device comprises: in the first measuring part (7) in the form of at least one Peltier element; and / or and / or formed as a temperature-controlled cover that can be placed on both measuring parts (7, 8); Both the measuring section and the sample are formed as a convection heating chamber and / or a convection cooling chamber, in which the temperature is controlled by gas or liquid, and / or A rheometer (100) in which the first measuring part (7) and the second measuring part (8) are arranged, characterized in that the rheometer is formed as a high-temperature furnace.

12. A rheometer (100) as described in claim 11, characterized in that the at least viscous sample (12) is liquid.

13. The rheometer (100) of claim 11, characterized in that the rheometer is a rotational rheometer.

14. A rheometer (100) as described in claim 11, characterized in that the control and processing unit is configured to calculate the density (ρ) of the sample (12) according to a method described in any one of claims 1 to 10.

15. the first measuring part (7) being configured as a measuring cup having an approximately cylindrical cross section, the second measuring part (8) is formed as a measuring body having an approximately cylindrical cross section, the outer diameter of the second measuring part (8) being smaller than the inner diameter of the first measuring part (7); The rheometer (100) according to any one of claims 11 to 14, characterized in that the first measuring part (7) and the second measuring part (8) are arranged coaxially in the rheometer (100), and a measuring gap (13) having a predetermined width can be formed between the concentric walls of the first measuring part (7) and the second measuring part (8).

16. A rheometer (100) as described in claim 15, characterized in that the measuring body is a rheology measuring spindle.

17. the rheometer (100) comprises at least one measuring motor (4) having a measuring shaft (14), the first measuring part (7) or the second measuring part (8) being connected to the measuring shaft (14), each measuring part (7, 8) being capable of a relative rotational and / or oscillatory movement with respect to the other measuring part (7, 8), The rheometer (100) according to any one of claims 11 to 16, characterized in that the control and processing unit is configured to define the rotation speed of the measurement motor (4) and to measure the torque occurring on the measurement shaft (14) and / or to define the torque of the measurement motor (4) and to measure the rotation speed of the measurement motor (4).

18. The rheometer (100) a first measuring motor (4) having a first measuring shaft (14), said first measuring part (7) being connected to said first measuring shaft (14), said first measuring part (7) being capable of performing a rotational and / or oscillatory movement, a second measuring motor (4') having a second measuring shaft (14'), said second measuring part (8) being connected to said second measuring shaft (14'), said second measuring part (8) being capable of performing a rotational and / or oscillatory movement independently of said first measuring part (7), The control and processing unit comprises: configured to determine the rotation speed of the first measuring motor (4) and / or the second measuring motor (4') in order to measure the torque acting on the first measuring shaft (14) and / or on the second measuring shaft (14'); and / or 18. The rheometer (100) according to any one of claims 11 to 17, characterized in that a torque of the first measuring motor (4) and / or the second measuring motor (4') is defined and the number of revolutions of the first measuring motor (4) and / or the second measuring motor (4') is measured.

19. the control and processing unit is configured to control a heating and / or cooling device; The rheometer (100) according to any one of claims 11 to 18, characterized in that the control and processing unit comprises a memory device and is configured to store in the memory device a volume correction curve and / or a volume correction table and / or a normal force correction curve and / or a normal force correction table determined by the method according to claim 1 or 4.

20. 19. The rheometer (100) according to claim 17 or 18, characterized in that the control and processing unit evaluates the measured values ​​obtained in connection with each of the measuring shafts (14) and / or each of the measuring motors (4) simultaneously with determining the density of the sample (12) and determines at least one rheological parameter of the sample (12).

21. A rheometer (100) as described in claim 20, characterized in that the rheological parameter is viscosity.

22. The normal force measuring unit (5) is connected to the first measuring part (7) and a further normal force measuring unit is connected to the second measuring part (8), which measures the normal force (F) between both measuring parts (7, 8) simultaneously with the normal force measuring unit (5). Ｎ 22. The rheometer (100) according to claim 11, characterized in that the second measuring part (8) is immersed in the sample (12) and the second measuring part (8) is immersed in the sample (12).

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