THERMOMETER HAVING A DIAGNOSTIC FUNCTION

Abstract

The present disclosure relates to a method for determining and/or monitoring the temperature of a medium by means of a thermometer having at least one temperature sensor, the method including: determining a measured value for the temperature of the medium by means of a temperature sensor; determining a heat flow, in particular heat dissipation, in the region of the temperature sensor; and determining a measured value deviation for the measured value for the temperature on the basis of a model for heat dissipation in the region of the temperature sensor.

Claims

1-13. (canceled)

14. A method for determining and/or monitoring a temperature of a medium using a thermometer, which includes a temperature sensor, the method comprising: determining a measured value of the temperature of the medium using the temperature sensor; determining a heat flow, or a variable associated with the heat flow, in a region of the temperature sensor; and determining a measured value deviation for the measured value of the temperature based on a model for heat flow in the region of the temperature sensor.

15. The method of claim 14, wherein the heat flow is a heat dissipation.

16. The method of claim 14, wherein a state indicator for the thermometer is determined based on the determined measured value deviation.

17. The method of claim 14, wherein: the thermometer comprises a temperature sensor comprising a temperature-sensitive sensor element electrically contacted via at least a first connection line and a second connection line; the first connection line is divided into a first section and a second section; the first section, which faces the sensor element, comprises a first material; the second section, which faces away from the sensor element, comprises a second material, which differs from the first material; the second connection line comprises the second material; and the first section of the first connection line and at least a portion of the second connection line define a first differential temperature sensor in the form of a thermocouple.

18. The method of claim 17, wherein the heat flow is determined using the differential temperature sensor.

19. The method of claim 16, wherein the state indicator is determined by comparing the determined measured value deviation with a reference value for the measured value deviation.

20. The method of claim 19, wherein the reference value for the measured value deviation is determined using the process when the thermometer is put into operation in the process.

21. The method of claim 19, further comprising making a statement about the state of the thermometer when a difference between the determined measured value deviation and the reference value exceeds or falls below a predefined limit value.

22. The method of claim 16, wherein, in the case of invasive temperature determination and/or monitoring, the state indicator is a statement about an installation condition, an occurrence of corrosion or a deposit formation and, in the case of non-invasive temperature determination and/or monitoring, the state indicator is a statement about a thermal coupling between the thermometer and a container containing the medium.

23. The method of claim 16, wherein the statement is a statement about a change or an exchange of the medium, about a change in a flow rate of the medium, a self-heating error in the region of the temperature sensor, or a change in a heat transfer coefficient.

24. The method of claim 14, wherein the model is a parametric model comprising at least one static and one dynamic term for determining the measured value deviation.

25. The method of claim 14, wherein at least one of the following is incorporated in the model via at least one coefficient of the model: an installation condition or mounting condition of the thermometer on a container containing the medium; a process condition of a process in which the thermometer is applied; a parameter or another characteristic variable relating to the thermometer; a further process variable of the medium; a flow rate of the medium; an ambient temperature or an environmental influence for the thermometer; and information about a physical and/or chemical property of the medium.

26. The method of claim 14, wherein at least one coefficient of the model is determined analytically or numerically.

27. The method of claim 14, wherein at least one coefficient is determined using a reference measurement using a reference device in a reference medium.

Description

[0034] The invention is explained in more detail based upon the following drawings. The following are shown:

[0035] FIG. 1: a schematic representation of a thermometer according to the prior art with a temperature sensor in the form of a resistance element; and

[0036] FIG. 2: exemplary embodiment of a thermometer with a differential temperature sensor for determining the heat flow.

[0037] In the figures, the same features are identified with the same reference signs.

[0038] FIG. 1 shows a schematic representation of a thermometer 1 with a immersion body 2, e.g., a protective tube, a measuring insert 3, and an electronics module 4 according to the prior art. The measuring insert 3 is introduced into the immersion body 2 and comprises a temperature sensor 5 which in the present case comprises a temperature-sensitive element in the form of a resistance element. The temperature sensor is electrically contacted via the connection lines 6 and connected to the electronics module 4. In other embodiments, the electronics module 4 can also be arranged separately from the measuring insert 3 and immersion body 2. In addition, the sensor element 5 need not necessarily be a resistance element, nor does the number of connection lines 6 used need necessarily be two. Rather, the number of connection lines 6 can be selected appropriately depending on the measurement principle used and the temperature sensor used.

[0039] As already explained, the measuring accuracy of a thermometer 1 depends to a large extent on the respective materials and on contacting means, in particular thermal contacting means, in particular in the region of the temperature sensor 5. The temperature sensor 5 is in thermal contact with the medium M indirectly, i.e., via the immersion body 2. The temperature sensor 5 is thus separated from the medium M by a plurality of thermal resistances. Depending on the process conditions and/or the respective structural design of the thermometer, it is therefore possible that there is no thermal equilibrium between the medium M and the thermometer at least temporarily and/or in part. As a result of the absence of a thermal equilibrium, temperature gradients ΔT.sub.1 or ΔT.sub.2 may arise, for example, in the region of the temperature sensor 5 or also along the connection lines 6, said temperature gradients distorting the temperature values measured in each case with the temperature sensor 5 as a result of resulting heat flows.

[0040] Temperature gradients ΔT.sub.1 in the region of the temperature sensor 5 are particularly relevant in this context. The present invention therefore enables the detection of such temperature gradients. This leads to a significantly improved measuring accuracy of the thermometer.

[0041] The same considerations apply analogously to a thermometer for the non-invasive determination and/or monitoring of the temperature.

[0042] FIG. 2 shows possible exemplary embodiments of a thermometer having a differential temperature sensor T.sub.2 for determining the heat flow. A temperature sensor T.sub.1 in the form of a resistance element 7 applied to a substrate 8 is used for determining and/or monitoring the temperature T of the medium M. The temperature sensor T.sub.1 is electrically contacted by means of the two connection lines 9 and 10 and is thus operated in the so-called two-conductor circuit. In the present case, both connection lines 9 and 10 are attached directly to the resistance element 7. However, it should be noted at this point that all contacting means known to the person skilled in the art are possible in principle for connecting the temperature sensor T.sub.1 to the connection lines 9 and 10.

[0043] The first connection line 9 is divided into a first section 9a and a second section 9b. The first section 9a consists of a first material, and the second section 9b and the second connection line 10 consist of a second material which differs from the first material. In this way, the first section 9a of the first connection line 9 and at least a part t of the second connection line 10 form a first differential temperature sensor T.sub.2 in the form of a thermocouple. The two materials for the first section 9a of the first connection line 9 and the second section 9b of the first connection line and for the second connection line 10 are selected in such a way that a thermovoltage can be detected by means of T.sub.2 due to a temperature difference between the points a and b and the different thermovoltages forming accordingly in the sections 9a and t due to the thermoelectric effect.

[0044] The first section 9a of the first connection line 9 is preferably short in comparison to the total length of the first connection line 9; for example, the length of the first section 9a of the first connection line 9 is in the range of a few millimeters or centimeters. In this way, it can be ensured that the values determined by means of the first differential temperature sensor T.sub.2 reflect a temperature gradient ΔT.sub.1 in the region of the temperature sensor T.sub.1 as far as possible.

[0045] In the example shown in FIG. 2a, the first connection line 9 and the second connection line 10 are separately attached to the resistance element. The first section 9a of the first connection line 9 and the part t of the second connection line 10 are thus indirectly connected via the resistance element 7. In another embodiment, however, the first section 9a of the first connection line 9 and the part t of the second connection line 10 could also be connected directly to one another and then attached to the temperature sensor T.sub.1. Of course, instead of the temperature sensor T.sub.1 shown by way of example here for all figures with a sensor element in the form of a resistance element 7, other temperature sensors well known to the person skilled in the art can also be used.

[0046] In the embodiment shown in FIG. 2b, the second connection line 10 is also divided into a first section 10a and a second section 10b. In this case, the first differential temperature sensor T.sub.2 is formed by the first sections 9a and 10a of the first connection line 9 and the second connection line 10. According to FIG. 2b, but not necessarily, the two first sections 9a and 10a of the two connection lines 9 and 10 are of the same length. In this case, the second sections 9b and 10b of the first connection line 9 and of the second connection line 10 are extension wires, preferably similarly designed extension wires. However, in the case of the embodiment according to FIG. 2a, it is also advantageous if the second section 9b of the first connection line 9 and the second connection line 10 are of similar design.

[0047] By means of the method according to the invention, a heat flow W is now determined by means of the differential temperature sensor T.sub.2 and a suitable model MOD for heat dissipation is provided by means of which a measured value deviation δT can be determined on the basis of the temperature gradient ΔT. By means of the measured value deviation δT, the measured values determined by the temperature sensor T.sub.1 can be corrected and/or adjusted, i.e. measurement errors can be compensated and/or state monitoring of the thermometer 1 can be carried out.

[0048] One possibility for a corresponding model is given by a parametric model in which a compensated temperature T.sub.ks of the medium is composed of a plurality of terms, such as for example:

[00001]$T_{\mathrm{ks}}=T+k_1+k_{2}W+k_3\frac{\mathrm{dT}}{\mathrm{dW}}$

[0049] Here, k.sub.1-k.sub.3 are coefficients of the model MOD which can be determined, for example, numerically, analytically or experimentally. With the model MOD, static thermal and dynamic thermal measured value deviations can be achieved by means of a regression Σ(T.sub.ks−T.sub.M).sup.2.fwdarw.0, where T.sub.M corresponds to the temperature of the medium M without the effect of a temperature gradient in the region of the temperature sensor.

[0050] An alternative for a suitable model MOD is, for example, one in which a variation of the measured value deviation δT over time is taken into account, such as, for example:

[00002]$T_{\mathrm{ks}}=T+k_1+k_{2}W+k_3\frac{\mathrm{dT}}{\mathrm{dW}}$

[0051] It is pointed out that, in addition to the two exemplary models indicated here, numerous further models MOD can be formed, which also fall under the present invention. For example, instead of the heat flow, a different variable, in particular a measured variable, representing the heat flow, for example a voltage, can also be used for the model MOD.

LIST OF REFERENCE SIGNS

[0052] 1 Thermometer [0053] 2 Immersion body [0054] 3 Measuring insert [0055] 4 Electronics module [0056] 5 Sensor element [0057] 6 Connecting wires [0058] 7 Resistance element [0059] 8 Substrate [0060] 9-10 First, second connection line [0061] 9a-10a First sections of the connection lines [0062] 9b-10b Second sections of the connection lines [0063] M Medium [0064] T Temperature [0065] T.sub.1 Temperature sensor [0066] ΔT.sub.1 Temperature gradient [0067] T.sub.2 Differential temperature sensor [0068] δT Measured value deviation [0069] T.sub.M Temperature medium M without temperature gradient [0070] T.sub.ks Compensated temperature [0071] MOD Heat dissipation model [0072] k, k.sub.1-k.sub.3 Coefficients of model MOD