Method and apparatus for calibrating a thermometer in situ

1. An apparatus for calibrating or validating a thermometer in situ, having:

a temperature sensor in the form of a resistance element for determining a temperature, wherein an electrical resistance of said resistance element is measured and thereby the temperature is determined; and

a reference element for calibrating said resistance element, wherein:

said reference element at least partially comprises a ferroelectric material, which experiences a phase transformation at least at one predetermined temperature in a temperature range relevant for calibrating or validating said resistance element; and

said resistance element and said reference element are integrated in a thermometer component and wherein said reference element is arranged next to the resistance element and is sufficiently close to the same temperature as the resistance element;

wherein said reference element comprises a capacitor element with a dielectric, and said ferroelectric material at least partially comprises the dielectric of said capacitor element.

2. The apparatus as claimed in claim 1 , wherein:

said ferroelectric material is a solid body.

3. The apparatus as claimed in claim 1 , wherein:

said ferroelectric material has a crystal structure; and

the crystal structure of said ferroelectric material changes in the phase transformation.

4. The apparatus as claimed in claim 1 , wherein:

the volume of said ferroelectric material changes in the phase transformation.

5. The apparatus as claimed in claim 1 , wherein:

said ferroelectric material has electrical or dielectric properties, which change in the phase transformation.

6. The apparatus as claimed in claim 1 , wherein:

the phase transformation, especially the change of the electrical or dielectric properties, of said ferroelectric material occurs abruptly at at least one predetermined temperature value.

7. The apparatus as claimed in claim 1 , wherein:

said ferroelectric material serves as a substrate for said temperature sensor.

8. The apparatus as claimed in claim 7 , wherein:

a phase transformation of the ferroelectric material of said carrier substrate from a ferroelectric state to a paraelectric state, or from a paraelectric state to a ferroelectric state and/or between different crystal structures occurs at at least one predetermined temperature.

9. The apparatus as claimed in claim 1 , wherein:

said ferroelectric material serves as a substrate for the resistance element manufactured in thin film technology or thick film technology.

10. The apparatus as claimed in claim 1 , wherein:

the predetermined temperature is a phase transformation temperature; and

the ferroelectric material is doped with impurity atoms, in order to influence the phase transformation temperature and/or the formation of crystal domains.

11. The apparatus as claimed in claim 1 , wherein:

the ferroelectric material is doped with divalent alkaline earth ions and/or transition metal ions, for the formation of uniform crystal domains.

12. The apparatus as claimed in claim 11 , wherein:

the doping with divalent alkaline earth ions and/or transition metal ions in the ferroelectric material is less than 1% of the ferroelectric material.

13. The apparatus as claimed in claim 1 , wherein:

the ferroelectric material is doped with strontium, lead and/or titanate, to influence the phase transformation temperature.

14. The apparatus as claimed in claim 13 , wherein:

the doping of the ferroelectric material with strontium, lead and/or titanate is up to 80% of the ferroelectric material.

15. The apparatus as claimed in claim 1 , wherein:

a voltage serving to polarize the ferroelectric material is applied to the ferroelectric material.

16. The apparatus as claimed in claim 7 , wherein:

said substrate serves as a carrier substrate, and

a voltage serving to polarize the carrier substrate is applied to the substrate, via a capacitor arrangement, which comprises two electrodes, between which the substrate is arranged.

17. The apparatus as claimed in claim 1 , wherein:

said temperature sensor and said reference element are arranged in a single sensor head.

18. A method for calibrating and/or monitoring the state of a temperature sensor or a thermometer in situ, comprising the steps of:

using a resistance element for determining the temperature by measuring an electrical resistance of said resistance element as temperature sensor; and

using a reference element for calibration and/or monitoring of the thermometer, wherein the reference element at least partially comprises a ferroelectric material; and

exposing said resistance element and said reference element to at least one predetermined temperature at which a phase transformation of the ferroelectric material occurs and evaluating measured values or measuring signals obtained by said temperature sensor or reference element, and using said measured values or measuring signals for calibrating and/or monitoring the state of the temperature sensor or thermometer;

wherein said reference element comprises a capacitor element with a dielectric, and said ferroelectric material at least partially comprises the dielectric of said capacitor element.

19. The method as claimed in claim 18 , further comprising the step of:

using a solid body as a ferroelectric material.

20. The method as claimed in claim 18 , wherein:

at the phase transformation of the solid body at least partially comprising the ferroelectric material, crystal structure, volume and/or dielectric or electrical properties of the ferroelectric material change, and at least one of these changes is used for calibrating the temperature sensor.

21. The method as claimed in claim 18 , wherein:

the temperature sensor and the reference element are essentially exposed to the same ambient temperature.

22. The method as claimed in claim 18 , wherein:

the thermometer is heated or cooled in order to induce the phase transformation of the ferroelectric material at the predetermined temperature.

23. The method as claimed in claim 18 , wherein:

a ferroelectric material doped with impurity atoms is used, in order to influence the phase transformation temperature and or the formation of crystal domains.

24. The method as claimed in claim 18 , wherein:

a ferroelectric material doped with divalent alkaline earth ions and/or transition metal ions is used for the formation of uniform crystal domains.

25. The method as claimed in claim 18 , wherein:

a ferroelectric material doped with strontium, lead and/or titanate is used, especially for influencing the phase transformation temperature.

26. The method as claimed in claim 18 , further comprising the step of:

applying a voltage serving to polarize the ferroelectric material to the ferroelectric material.

27. The method as claimed in claim 18 , further comprising the step of:

applying a voltage serving to polarize the carrier substrate to the substrate, especially by means of a capacitor arrangement, which comprises two electrodes, between which the substrate is arranged.

28. An apparatus for calibrating or validating a thermometer in situ, having:

a temperature sensor in the form of a resistance element for determining a temperature wherein an electrical resistance of said resistance element is measured and thereby the temperature is determined; and

a reference element for calibrating said temperature sensor resistance element, wherein:

said reference element at least partially comprises a ferroelectric material, which experiences a phase transformation at least at one predetermined temperature in a temperature range relevant for calibrating said temperature sensor resistance element;

said resistance element and said reference element are integrated in a thermometer component; and

said reference element and the resistance element are integrated into one sensor structure;

wherein said reference element comprises a capacitor element with a dielectric, and said ferroelectric material at least partially comprises the dielectric of said capacitor element.