Device and method for the in-situ calibration of a thermometer

1. An apparatus for determining and/or monitoring a temperature of a liquid, comprising:

a temperature sensor;

a reference element for in-situ calibration and/or validation of the temperature sensor; and

an electronics unit,

wherein the reference element is composed at least partially of a material in which a phase transformation occurs at a first predetermined phase transformation temperature in a temperature range relevant for calibrating the temperature sensor,

wherein the material is ferroelectric material, and the phase transformation includes a change in a permittivity of the ferroelectric material; or the material is a ferromagnetic material, and the phase transformation includes a change in a magnetic permeability of the ferromagnetic material; or the material is a superconducting material, and the phase transformation includes a change in a conductivity of the material,

wherein in the phase transformation the material remains in the solid phase, and

wherein the electronics unit is embodied to:

supply the reference element and the temperature sensor with a dynamic excitation signal that is a time-varying alternating electrical current or a time-varying alternating voltage;

receive a dynamic signal from the temperature sensor and determine the temperature of the liquid therefrom;

receive a dynamic signal from the reference element and detect the phase transformation in the reference element therefrom by detecting the change in the permittivity of the ferroelectric material or the change in the magnetic permeability of the ferromagnetic material or the change in the conductivity of the superconducting material; and

when the phase transformation is detected, compare the phase transformation temperature with the determined temperature and perform a calibration of the temperature sensor based on the comparison of the phase transformation temperature and the determined temperature.

2. The apparatus as claimed in claim 1 ,

wherein the excitation signal and/or a received signal received from the reference element is, in each case, a sinusoidal, rectangular, triangular, sawtooth-shaped, or pulse-shaped electrical current or voltage signal.

3. The apparatus as claimed in claim 1 ,

wherein the electronics unit is embodied to vary the frequency and/or the amplitude of the excitation signal.

4. The apparatus as claimed in claim 1 ,

wherein the material is the ferroelectric material, and

wherein the reference element is a capacitor element having a dielectric composed at least partially of the material in which the phase transformation occurs.

5. The apparatus as claimed in claim 1 ,

the material is the ferromagnetic material, and

wherein the reference element includes a coil arrangement having at least one coil and a magnetically conductive body, wherein the magnetically conductive body is composed at least partially of the material in which the phase transformation occurs.

6. The apparatus as claimed in claim 1 ,

wherein the electronics unit is further embodied to ascertain an impedance, or a variable dependent on the impedance, of at least one component of the reference element, and to detect the phase transformation based on the impedance, or the variable dependent on the impedance, based on a line or a curve of the impedance, or the variable dependent on the impedance, as a function of time and/or temperature.

7. The apparatus as claimed in claim 1 ,

the material is the ferroelectric material or the ferromagnetic material, and

wherein the electronics unit is further embodied to ascertain a capacitance, an inductance, or a variable dependent on the capacitance and/or the inductance, of at least one component of the reference element, and to detect the phase transformation based on the capacitance, the inductance or the variable dependent on the capacitance and/or the inductance, based on a line or a curve of the capacitance, the inductance or the variable dependent on the capacitance and/or the inductance, as a function of time and/or temperature.

8. The apparatus as claimed in claim 1 ,

wherein the electronics unit includes a bridge circuit, including a Wien bridge or a Wien-Maxwell bridge, and the reference element is a component of the bridge circuit.

9. The apparatus as claimed in claim 1 ,

wherein the electronics unit includes an electrical oscillatory circuit, and the reference element is a component of the oscillatory circuit.

10. The apparatus as claimed in claim 9 ,

wherein the electronics unit is further embodied to detect the phase transformation based on a change of a resonant frequency of the oscillatory circuit.

11. The apparatus as claimed in claim 1 , further comprising:

a means for applying an electrical field or a magnetic field,

wherein the electronics unit is further embodied to measure over time an output voltage of the electronics unit and to plot the measured output voltage as a function of the dynamic excitation signal to form a hysteresis diagram, and

wherein the electronics unit is further embodied to detect the phase transformation based on the hysteresis diagram.

12. A method for in-situ calibration and/or validation of an apparatus for determining and/or monitoring a temperature of a liquid, comprising:

providing the apparatus for determining and/or monitoring the temperature of the liquid, including:

a temperature sensor;

a reference element for the in-situ calibration and/or validation of the temperature sensor; and

an electronics unit,

wherein the reference element is composed at least partially of a material in which a phase transformation occurs at a first predetermined phase transformation temperature in a temperature range relevant for calibrating the temperature sensor,

wherein the material is ferroelectric material, and the phase transformation includes a change in a permittivity of the ferroelectric material; or the material is a ferromagnetic material, and the phase transformation includes a change in a magnetic permeability of the ferromagnetic material; or the material is a superconducting material, and the phase transformation includes a change in a conductivity of the material,

wherein in the phase transformation the material remains in the solid phase, and

wherein the electronics unit is embodied to:

supply the reference element and the temperature sensor with a dynamic excitation signal that is a time-varying alternating electrical current or a time-varying alternating voltage;

receive a dynamic signal from the temperature sensor and determine the temperature of the liquid therefrom;

receive a dynamic signal from the reference element and detect the phase transformation in the reference element therefrom by detecting the change in the permittivity of the ferroelectric material or the change in the magnetic permeability of the ferromagnetic material or the change in the conductivity of the superconducting material; and

when the phase transformation is detected, compare the phase transformation temperature with the determined temperature and perform a calibration of the temperature sensor based on the comparison of the phase transformation temperature and the determined temperature;

supplying the reference element and the temperature sensor with the dynamic excitation signal;

receiving the dynamic signal from the temperature sensor and determining the temperature of the liquid therefrom;

receiving the dynamic signal from the reference element and detecting the phase transformation in the reference element therefrom by detecting the change in the permittivity of the ferroelectric material or the change in the magnetic permeability of the ferromagnetic material or the change in the conductivity of the superconducting material; and

when the phase transformation is detected, comparing the phase transformation temperature with the determined temperature and performing the calibration of the temperature sensor based on the comparison of the phase transformation temperature and the determined temperature.