ASSESSING THE MEASUREMENT QUALITY OF THE SENSOR ELEMENT FOR MEASURING AN OBJECT TEMPERATURE

Abstract

The present disclosure includes a sensor element for registering temperature of an object, which includes: a substrate, wherein the substrate includes a platform face, which defines a first plane; a temperature detector, which is applied on a first temperature plane on the substrate and which is embodied to register the temperature of the object, wherein the first temperature plane lies in the first plane or essentially in parallel with the first plane; at least one sensor applied on a first subregion of the substrate for determining a temperature difference within the first subregion; and a passivation, which is applied on the substrate and which covers the substrate, the temperature detector and the sensor for determining the temperature difference, as well as residing in a method for assessing measurement quality of a sensor element of the present disclosure.

Claims

1-17. (canceled)

18. A sensor element for registering temperature of an object, the sensor element comprising: a substrate including a platform face, which defines a first plane; a temperature detector applied on the substrate in a first temperature plane and configured to register the temperature of the object, wherein the first temperature plane lies in the first plane or substantially parallel to the first plane; at least one temperature sensor applied on a first subregion of the substrate and configured to determine a temperature difference within the first subregion; and a first passivation applied on the substrate as to cover the substrate, the temperature detector and the at least one temperature sensor.

19. The sensor element of claim 18, wherein the at least one temperature sensor comprises a first thermocouple, which comprises a conductor pair of different materials, wherein the conductor pair includes a contacting point in the first temperature plane and a reference point separated at a distance from the contacting point, and wherein the first thermocouple is configured as to produce an output voltage, which represents a measure for a temperature difference between the contacting point and the reference point.

20. The sensor element of claim 19, wherein the first thermocouple is mounted such that both the contacting point and the reference point lie in the first temperature plane.

21. The sensor element of claim 19, wherein the first thermocouple is mounted such that the reference point lies in a temperature plane other than the first temperature plane.

22. The sensor element of claim 19, wherein the at least one temperature sensor includes at least one other thermocouple, which is connected electrically in series with the first thermocouple and which is arranged such that a contacting point of the at least one other thermocouple lies in the first temperature plane and a reference point of the at least one other thermocouple lies in the first temperature plane or in a temperature plane other than the first temperature plane.

23. The sensor element of claim 18, comprising at least one temperature sensor applied on a second subregion of the substrate and configured to determine a temperature difference within the second subregion, wherein the second subregion is different than the first subregion.

24. The sensor element of claim 18, further comprising a cover layer applied substantially completely over the first passivation or over a second passivation applied on the first passivation.

25. The sensor element of claim 24, wherein the cover layer comprises a heat reflecting material or a heat absorbing material.

26. The sensor element of claim 18, further comprising an encapsulation comprising a heat conductive material and disposed such that the encapsulation substantially completely covers and heat conductively contacts the first passivation and the substrate and, thereby, the object.

27. The sensor element of claim 18, further comprising a cooling and/or heating unit mounted in a different temperature plane parallel to the first temperature plane.

28. The sensor element of claim 27, wherein the cooling and/or heating unit comprises a thermistor and/or thermoelectric material.

29. The sensor element of claim 18, wherein the temperature detector is a thermistor and comprises a material having a defined temperature coefficient.

30. The sensor element of claim 29, wherein the material of the temperature detector is platinum or nickel.

31. The sensor element of claim 22, wherein the first thermocouple and/or the at least one other thermocouple comprise of compound semiconductor.

32. The sensor element of claim 18, wherein the passivation comprises a glass, a ceramic material or a plastic.

33. A method for assessing measurement quality of the sensor element according to claim 18, wherein the sensor element is connected with an operation/evaluation unit, the method comprising: thermally contacting a surface of the object with the sensor element thermally; registering a temperature of the object with the operation/evaluation unit via the temperature detector; and registering an output voltage of the at least one temperature sensor with the operation/evaluation unit.

34. The method of claim 33, wherein the sensor element further comprises a cooling and/or heating unit mounted in a different temperature plane parallel to the first temperature plane, the method further comprising: supplying electrical power to the cooling and/or heating unit via the operation/evaluation unit as a function of the registered output voltage to cool and/or heat the sensor element.

35. The method of claim 33, further comprising: calculating a true temperature of the object based on the registered output voltage using the operation/evaluation unit.

Description

[0050] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0051] FIG. 1 a first example of an embodiment of a sensor element of the invention;

[0052] FIG. 2 a second example of an embodiment of a sensor element of the invention;

[0053] FIG. 3 a third example of an embodiment of a sensor element of the invention;

[0054] FIG. 4 a first variant of the invention for passive reduction of heat flows;

[0055] FIG. 5 a second variant of the invention for active reduction of heat flows;

[0056] FIG. 6 an example of an embodiment for compensating heat flows; and

[0057] FIG. 7 a fourth example of an embodiment of a sensor element of the invention.

[0058] FIG. 1 shows in cross-section a schematic view of a first example of an embodiment of a sensor element 1 of the invention. The sensor element 1 is composed of a planar substrate 100, for example, a ceramic substrate, for example, Al.sub.2O.sub.3. The upper surface of the substrate defines a first plane in x and y directions. Applied on the substrate 100 per thin film or thick film technology is a temperature detector 110. Temperature detector 110 is especially a thermistor. Temperature detector 110 is embodied as meander-shaped, such as shown in FIG. 3, and is electrically suppliable via contact pads 111. Applied on the substrate 100 and on the temperature detector 110, especially per thick film technology, are first and second passivations 130, 131. The passivations 130, 131 are especially of the same material, for example, a glass, a ceramic material or a plastic (for example, polyimide, SiO.sub.2 or Al.sub.2O.sub.3). They are, however, produced in two different manufacturing steps. The structuring of the passivations 130, 131, for example, in the form of holes for below described thermocouples 120 or contact pads, occurs, for example, via a lithography and/or etching method.

[0059] The bottom face of the substrate 100 of the sensor element 1 is connected with an object 2, whose temperature is to be determined. For this, a connecting layer 170 is provided, for example, an adhesive layer, a sintered layer or a solder layer, which establishes a heat conducting bond between the substrate 110 and the object 2. The object 2 is, for example, a carrier, especially a small plate or a small tube, which is in contact with a measured medium. It can, however, also be a less generic object 2, for example, a housing of a pump, to which the substrate is secured.

[0060] In such a construction, there arise, because of the different materials, a plurality of temperature planes T0, T1, T2, T3, T4, which lie essentially parallel with the first plane defined by the substrate. The temperature plane T0 is the surface temperature of the object 2. The temperature plane T1 is the transition between the connecting layer 170 and the substrate 110. The temperature plane T2, also referred to as first temperature plane, is that temperature plane, in which the temperature detector 110 lies and whose temperature the temperature detector 110 registers.

[0061] The temperature plane T3 lies in the transition between the two passivations 130, 131. The temperature plane T4 lies on the upper surface of the upper passivation 131.

[0062] This basic sensor construction forms the basis for all examples of embodiments described in the following.

[0063] The materials of the sensor element 1 are selected in such a manner that the absolute temperature difference between the individual temperature planes T0, T1 is very small, or negligible, and, thus, the temperature detector 110 is in good thermal contact with the object 2. Along with this, the materials of the passivations 130, 131 are so selected or so embodied that the temperature detector is insulated as well as possible from the environment. Under ideal measuring conditions, there are no heat flows in the component, neither in the x-y plane nor in the z direction. In such case, temperature measured by the temperature detector 110 corresponds to the temperature of the object to be measured. As a result of the, as a rule, different temperatures of the component surface (here temperature plane T4) and the environment (for example, air) and/or as a result of heat input, or heat loss, from the contacting wires (not shown), local heat flows occur, which produce local temperature differences in the component. This cannot be detected by the temperature detector 110, since, first, the temperature detector 110 only delivers an absolute temperature value without comparison and, second, the temperature detector 110 registers an integral value integrated over the area spanned by it. Such can lead to the fact that the temperature measured by the temperature detector 110 differs from the true, absolute temperature of the object 2.

[0064] To overcome this problem, according to the invention, at least one other sensor, for instance, in the form of a thermocouple 120, is integrated into the sensor element 1. The thermocouple is composed of two conductors, which meet in a shared reference point RP and which have a contacting point KP, via which the thermocouple 120 can be electrically contacted. Thermocouple 120 is integrated into the first passivation 130. In the example of an embodiment shown in FIG. 1, first, the first passivation 130 is applied. Thereafter, the passivation 130 is provided with holes, into which the thermocouple 120 is installed. Then, the second passivation 131 is applied. The contacting point KP of the thermocouple is located thereby in the first temperature plane T2, while the reference point RP is located in the temperature plane T3. The conductors of the thermocouple are made of mutually differing materials, for example, two different compound semiconductors. As a result of this manner of construction, thermocouple 120 produces an output voltage, which results from a temperature difference between the reference point RP and the contacting point KP and which is proportional to the size of the temperature difference. The output voltage is registrable via separate contact pads 112. In the present case, the thermocouple registers a temperature difference between the temperature plane T3 and the temperature plane T2, where the temperature detector is located. Thus, a heat flow is registrable in the z direction, thus, orthogonally to the temperature planes T0, T1, T2, T3, T4, and, thus, to the first plane. The output voltage depends on the temperature difference as follows:

U=S*(T3−T2)

[0065] where S refers to the thermoelectric coefficient of the material combination of two conductors (units μV/K).

[0066] The higher the output voltage, the higher is the temperature difference between the temperature planes T2 and T3. Correspondingly poorer is the informational quality of the temperature registered by the temperature detector 110, and the greater the deviation of the temperature registered by the temperature detector 110 from the true temperature of the object 2.

[0067] FIG. 2 shows another example of an embodiment. In such case, a plurality of thermocouples 120, 120′ are used, whose contacting points KP, KP′ lie, in each case, in the temperature plane T2 and whose reference points RP lie, in each case, in the temperature plane T3. The thermocouples are arranged at different sites on the platform plane in x and/or y direction. In such case, there are, in principle, two circuit types: [0068] 1) The plurality of thermocouples 120, 120′ are connected serially together. In this way, the output voltages of all thermocouples add to a common output voltage, which can be taken via the contact pads 112. Such a serial circuit increases the sensitivity of registering heat flows. The heat flow in the z direction is, in such case, however, not locally determinable, but is, instead, integrated over the area spanned by the thermocouples. [0069] 2) Each of the thermocouples is separately contactable and delivers its own output voltage. For this, each of the thermocouples has separate contact pads. The substrate is thereby divided into a plurality of subregions SR1, SR2, . . . , SRn. In this way, a plurality of local heat flows are registrable, since each of the thermocouples detects a local heat flow of its subregion SR1, SR2, . . . , SRn. It is also possible per subregion SR1, SR2, . . . , SRn to provide pluralities of serially connected thermocouples, in order to increase the sensitivity. [0070] 3) A combination of 1) and 2): [0071] Each of the subregions SR1, SR2, . . . , SRn has a plurality of thermocouples, which are serially connected in the subregions SR1, SR2, . . . , SRn. In this way, the sensitivity is increased for registering heat flows in each separate subregion SR1, SR2, . . . , SRn.

[0072] Especially advantageously, the thermocouples are arranged raster-like or matrix-like. In this way, sites can be relatively exactly detected, where the sensor element 1 has local defects. For example, a map can be formed, by means of which the values of heat flows are displayed as a function of location.

[0073] The sensor element shown in the plan view of FIG. 3 includes thermocouples 120, 121, whose reference points RP, RP′ and contacting points KP, KP′ lie in the same temperature plane T3. In this way, a heat flow in x and/or y direction is detectable. As shown, the thermocouples 120, 120′ are connected together in series. In this way, the output voltages of all thermocouples add to a common output voltage, which can be accessed via the contact pads 112. Also in such case, it is, however, possible to provide that each of the thermocouples is separately contactable via its own contact pads and delivers its own output voltage. Also in such case, the division into different subregions SR1, SR2, . . . , SRn is possible, which are provided with one or more separate thermocouples.

[0074] FIG. 4 shows a first option for reducing heat flows. Such is usable for all previously shown forms of embodiment of the sensor element 1, as well as for the example of an embodiment shown in FIG. 7. In particular, a cover layer 140 is applied on the second passivation 131.

[0075] Such is composed, for example, of a heat reflecting material, for example, gold or silver. This leads to a reflection of arriving radiation and prevents, moreover, that heat due to unwanted heat flows escapes from the passivation 131. This enables that the temperature measured by the temperature detector is closer to the true temperature of the object.

[0076] Alternatively, the cover layer 140 is composed of a heat absorbing material. Advantageous are porous, inert materials, such as black-gold, platinum or metal oxides. In-coupling of radiation from the environment is resisted by the surface configuration in the particular application.

[0077] FIG. 5 shows a second opportunity for reducing heat flows. Instead of the cover layer 140, an encapsulation 150 is provided, which is arranged in such a manner that it essentially completely covers and heat conductively contacts the upper passivation 131 and that it heat conductively contacts the substrate 100, and, especially, the object 2. The encapsulation 150 forms a type of “thermal shield” for measured objects of high heat capacity. The measured object acts, in such case, as a heat sink. Used as encapsulation is, for example, a metal tube or a solid plate of a metal material.

[0078] An embodiment for active compensation of heat flows is shown in FIG. 6. Such is again usable for all previously shown forms of embodiment of the sensor element 1, as well as for the example of an embodiment shown in FIG. 7 and is also combinable with the reduction mechanisms shown in FIGS. 4 and 5.

[0079] In this case, a cooling and/or heating unit 160 is provided, which is suppliable with electrical energy via separate contact pads. By the supplying of the electrical energy, the cooling and/or heating unit 160 produces heat or else it cools its surroundings. Suitable as heating unit is especially a thermistor or heating wire. Suitable as cooling unit is especially a thermoelectric Peltier cooler. The cooling and/or heating unit 160 is arranged in a temperature plane other than that containing the thermocouples.

[0080] Especially, the cooling and/or heating unit 160 includes a control unit, which increases the heating power, or cooling power, until the heat loss produced by the heat flows is significantly reduced (such is detected by means of the sensor by a temperature difference becoming smaller), or is compensated (in such case, a temperature difference is no longer detected by means of the sensor).

[0081] There can also be provided for each of the subregions SR1, SR2, . . . , SRn an independent, separate cooling and/or heating unit 160, which selects the heating power, or cooling power in accordance with the temperature difference detected in its subregion SR1, SR2, . . . , SRn.

[0082] FIG. 7 shows a final, alternative example of an embodiment of a sensor element 1 of the invention. Instead of one or more thermocouples, a further temperature detector is provided as a sensor 120. This must, in contrast to a thermocouple, however, be supplied with an electrical voltage, in order to produce a measurement signal. By means of the further temperature detector, an absolute temperature of the temperature plane, in which the temperature detector is arranged, is registrable. When this differs from the temperature registered by the temperature detector in the temperature plane T2, then a (e.g., unwanted) heat flow is present.

[0083] Common to all examples of embodiments is that an unwanted heat flow is detectable based on a temperature difference between different temperature planes, or different sites on the same temperature plane. It must be considered, however, that alone from the separation of the temperature planes from one another, a temperature difference can occur, without that the sensor element 1 is defective or the adhesive bond to the object 2 is defective. In such case, reference values can be registered earlier or in situ. If the registered temperature difference differs from these reference values over the course of operating time of a sensor element or in the case of construction of a plurality of different sensor elements 1, then such can be an indicator of unwanted heat flow. The cause of this can be, for example, a temporal change of the contacting layer 170, for example, due to delamination, and/or a defective contacting of a sensor element 1.

[0084] For all forms of embodiment, alternatively also a flexible substrate, for example, a film, or a curved substrate, can be used. The platform face, and therewith the first plane, can, in such case, thus, be curved. The additional planes, or temperature planes T0, T1, T2, T3, T4 are then oriented in parallel with such curved plane.

LIST OF REFERENCE CHARACTERS

[0085] 1 sensor element [0086] 100 substrate [0087] 110 temperature detector [0088] 111, 112 contact pads [0089] 120, 121 sensor for determining a temperature difference [0090] 130 first passivation [0091] 131 second passivation [0092] 140 cover layer [0093] 150 encapsulation [0094] 160 cooling and/or heating unit [0095] 170 connecting layer for coupling to the object to be measured [0096] 2 object [0097] RP, RP′ reference point [0098] KP, KP′ contacting point [0099] T0, T1, T2, T3, T4 temperature planes [0100] SR1, SR2, SRn subregions of the substrate [0101] C1, C2 conductor pair