Electronic circuit for driving a thermocouple element, temperature sensing device, and method for observing a leakage resistance of the thermocouple element

Patent metadata

Field	Value
Publication number	US-11143560-B2
Application number	US-201716464827-A
Country	US
Kind code	B2
Filing date	Nov 16, 2017
Priority date	Dec 8, 2016
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

Various embodiments include an electronic circuit for driving a thermocouple element comprising: contact electrodes for connecting cold-end electrodes of the thermocouple element; and a measurement circuit to measure a thermo-voltage generated by the thermocouple element. One of the electrodes is connected to a supply voltage and a ground potential over a voltage divider having resistors with pre-defined resistance values such that a common mode voltage between the contact electrode and the ground potential is in a pre-defined range. If a leakage resistance effective between the contact electrode and the ground potential is greater than a pre-defined threshold, a processor compares the common mode voltage to the pre-defined range and generates a calibration value for the measurement circuitry if the common mode voltage is outside the range.

First claim

What is claimed is:

1. An electronic circuit for driving a thermocouple element, the electronic circuit comprising:
contact electrodes for connecting cold-end electrodes of the thermocouple element;
a measurement circuit to measure a thermo-voltage generated by the thermocouple element between the contact electrodes as a function of a temperature difference between the cold-end electrodes and a hot-end side of the thermocouple element; and
a processor;
wherein one of the contact electrodes is connected to a supply voltage and to a ground potential of the electronic circuit over a voltage divider having resistors with pre-defined resistance values such that a common mode voltage between the contact electrode and the ground potential is in a pre-defined range;
if a leakage resistance effective between the contact electrode and the ground potential is greater than a pre-defined threshold, the processor compares the common mode voltage to the pre-defined range and generates a calibration value for the measurement circuitry if the common mode voltage is outside said pre-defined range.

2. An electronic circuit according to claim 1 , wherein the calibration value depends on a model describing a functional relationship between the leakage resistance and the common mode voltage.

3. An electronic circuit according to claim 1 , wherein the contact electrode is connected to a measurement electrode of the measurement circuit over a switch configured to alternately connect the measurement electrode to the contact electrode and to the ground potential; and
further comprising a control circuit configured to actuate the switch so the measurement circuit alternately measures the thermo-voltage and the common mode voltage.

4. An electronic circuit according to claim 1 , further comprising a connection switch connected to the contact electrodes to provide a short circuit between the contact electrodes when the connection switch is closed.

5. An electronic circuit according to claim 1 , wherein the processor is configured to generate a warning signal if it detects a low leakage resistance value.

6. An electronic circuit according to claim 1 , further comprising a ground contact electrode for connecting a sheath of a mineral-insulated cable of the thermocouple element to the ground potential.

7. A temperature sensing device comprising:
a thermocouple element;
contact electrodes for connecting cold-end electrodes of the thermocouple element;
a measurement circuit to measure a thermo-voltage generated by the thermocouple element between the contact electrodes as a function of a temperature difference between the cold-end electrodes and a hot-end side of the thermocouple element;
wherein one of the contact electrodes is connected to a supply voltage and to a ground potential of the electronic circuit over a voltage divider having resistors with pre-defined resistance values such that a common mode voltage between the contact electrode and the ground potential is in a pre-defined range, if a leakage resistance effective between the contact electrode and the ground potential is greater than a pre-defined threshold; and
a processor to compare the common mode voltage to the pre-defined range and to generate a calibration value for the measurement circuitry if the common mode voltage is outside said pre-defined range.

8. A method for determining a temperature related signal using a thermocouple element and observing a leakage resistance of the thermocouple element, the method comprising:
measuring a thermo-voltage generated by the thermocouple element between contact electrodes as a function of a temperature difference between the cold-end electrodes and a hot-end side of the thermocouple element;
wherein one of the contact electrodes is connected to a supply voltage and a ground potential of an electronic circuit over a voltage divider having resistors with pre-defined resistance values;
generating a common mode voltage with the voltage divider between the contact electrode and the ground potential, wherein the common mode voltage is in a pre-defined range;
if a leakage resistance effective between the contact electrode and the ground potential exceeds a pre-defined threshold, comparing the common mode voltage to the pre-defined range; and
if the common mode voltage is outside said pre-defined range, generating a calibration value for calibrating the measurement circuit.

9. An electronic circuit according to claim 1 , wherein the calibration value depends on a model describing a functional relationship between the leakage resistance and the thermo-voltage.

Assignees

• Cpt Group Gmbh
• Vitesco Tech Gmbh

Inventors

• Scotto Pierre

Classifications

• G01K7/021 Primary

  Particular circuit arrangements (G01K7/026, G01K7/12, G01K7/14 take precedence) · CPC title

• G01K7/026

  Arrangements for signalling failure or disconnection of thermocouples · CPC title

• G01K7/10 Primary

  Arrangements for compensating for auxiliary variables, e.g. length of lead · CPC title

• G01K7/02

  using thermoelectric elements, e.g. thermocouples · CPC title

• G01K15/005

  Calibration · CPC title