Temperature input unit, temperature measuring device, and recording medium

Patent metadata

Field	Value
Publication number	US-11307101-B2
Application number	US-201917417791-A
Country	US
Kind code	B2
Filing date	Jun 17, 2019
Priority date	Jun 17, 2019
Publication date	Apr 19, 2022
Grant date	Apr 19, 2022

Abstract

A temperature input unit includes a disconnection detection circuit that measures a temperature of a measurement target with at least one of a thermocouple or a temperature measurement resistor and feeds a disconnection detection current for disconnection detection to the thermocouple and a compensating wire connected to the thermocouple. A controller controls, before measuring the temperature of the measurement target with the thermocouple, a terminal switch and an input circuit switch to connect the compensating wire to a temperature measurement resistor input circuit and an A/D converter, and calculates a predicted value of a voltage drop resulting from resistance of the compensating wire occurring in response to the disconnection detection current. The controller controls the terminal switch and the input circuit switch to connect the compensating wire to a thermocouple input circuit and the A/D converter, and subtracts the predicted value from a measured value of the thermoelectromotive force detected by the thermocouple input circuit to calculate a corrected measured value of the thermoelectromotive force.

First claim

The invention claimed is:

1. A temperature input circuitry to measure a temperature of a measurement target with at least one of a thermocouple or a temperature measurement resistor, the temperature input circuitry comprising:
a disconnection detector to feed a disconnection detection current for disconnection detection to the thermocouple and a compensating wire connected to the thermocouple in a case of measurement of the temperature with the thermocouple;
a thermocouple detection circuit to detect a thermoelectromotive force of the compensating wire and the thermocouple both connected to the temperature input circuitry in the case of measurement of the temperature with the thermocouple;
a temperature measurement resistor detection circuit to feed a constant current to the temperature measurement resistor, which is connected to the temperature input circuitry, and to detect a resistance of the temperature measurement resistor in a case of measurement of the temperature with the temperature measurement resistor;
a connection switch to connect the compensating wire to the thermocouple detection circuit or the temperature measurement resistor detection circuit; and
a measurer to calculate the temperature of the measurement target based on the thermoelectromotive force detected by the thermocouple detection circuit in the case of measurement of the temperature with the thermocouple, and to calculate the temperature of the measurement target based on the resistance of the temperature measurement resistor detected by the temperature measurement resistor detection circuit in the case of measurement of the temperature with the temperature measurement resistor,
wherein the measurer
controls, before measuring the temperature of the measurement target with the thermocouple, the connection switch to connect the compensating wire to the temperature measurement resistor detection circuit, and calculates a predicted value of a voltage drop resulting from a resistance of the compensating wire occurring in response to the disconnection detection current, and
controls the connection switch to connect the compensating wire to the thermocouple detection circuit, and subtracts the predicted value from a measured value of the thermoelectromotive force detected by the thermocouple detection circuit to calculate a corrected measured value of the thermoelectromotive force detected by the thermocouple detection circuit and based on which the measurer calculates the temperature of the measurement target.

2. The temperature input circuitry according to claim 1 , wherein the measurer calculates the measured value while the thermocouple is connected to the compensating wire.

3. The temperature input circuitry according to claim 1 , wherein the measurer calculates a resistance value of the compensating wire with the temperature measurement resistor detection circuit, and calculates the predicted value based on the resistance value and a current value of the disconnection detection current.

4. The temperature input circuitry according to claim 3 , wherein the measurer calculates the measured value while the thermocouple is connected to the compensating wire.

5. A temperature measuring device to measure a temperature of a measurement target with at least one of a thermocouple or a temperature measurement resistor, the temperature measuring device comprising:
a disconnection detector to feed a disconnection detection current for disconnection detection to the thermocouple and a compensating wire connected to the thermocouple in a case of measurement of the temperature with the thermocouple;
a thermocouple detection circuit to detect a thermoelectromotive force of the compensating wire and the thermocouple both connected to the temperature measuring device in the case of measurement of the temperature with the thermocouple;
a temperature measurement resistor detection circuit to feed a constant current to the temperature measurement resistor, which is connected to the temperature measuring device, and to detect a resistance of the temperature measurement resistor in a case of measurement of the temperature with the temperature measurement resistor;
a connection switch to connect the compensating wire to the thermocouple detection circuit or the temperature measurement resistor detection circuit; and
a measurer to calculate the temperature of the measurement target based on the thermoelectromotive force detected by the thermocouple detection circuit in the case of measurement of the temperature with the thermocouple, and to calculate the temperature of the measurement target based on the resistance of the temperature measurement resistor detected by the temperature measurement resistor detection circuit in the case of measurement of the temperature with the temperature measurement resistor,
wherein the measurer
controls, before measuring the temperature of the measurement target with the thermocouple, the connection switch to connect the compensating wire to the temperature measurement resistor detection circuit, and calculates a predicted value of a voltage drop resulting from a resistance of the compensating wire occurring in response to the disconnection detection current, and
controls the connection switch to connect the compensating wire to the thermocouple detection circuit, and subtracts the predicted value from a measured value of the thermoelectromotive force detected by the thermocouple detection circuit to calculate a corrected measured value of the thermoelectromotive force detected by the thermocouple detection circuit and based on which the measurer calculates the temperature of the measurement target.

6. The temperature measuring device according to claim 5 , wherein the measurer calculates the measured value while the thermocouple is connected to the compensating wire.

7. The temperature measuring device according to claim 5 , wherein the measurer calculates a resistance value of the compensating wire with the temperature measurement resistor detection circuit, and calculates the predicted value based on the resistance value and a current value of the disconnection detection current.

8. The temperature measuring device according to claim 7 , wherein the measurer calculates the measured value while the thermocouple is connected to the compensating wire.

9. A non-transitory computer readable recording medium storing a program executable by a temperature measuring device that measures a temperature of a measurement target with at least one of a thermocouple or a temperature measurement resistor, the temperature measuring device including:
a disconnection detector to feed a disconnection detection current for disconnection detection to the thermocouple and a compensating wire connected to the thermocouple in a case of measurement of the temperature with the thermocouple,
a thermocouple detection circuit to detect a thermoelectromotive force of the compensating wire and the thermocouple both connected to the temperature measuring device in the case of measurement of the temperature with the thermocouple,
a temperature measurement resistor detection circuit to feed a constant current to the temperature measurement resistor, which is connected to the temperature measuring device, and to detect a resistance of the temperature measurement resistor in a case of measurement of the temperature with the temperature measurement resistor,
a connection switch to connect the compensating wire to the thermocouple detection circuit or the temperature measurement resistor detection circuit, and
a measurer to calculate the temperature of the measurement target based on the thermoelectromotive force detected by the thermocouple detection circuit in the case of measurem

Assignees

• Mitsubishi Electric Corp

Inventors

• Yamashita Kohei

Classifications

• G01K7/10 Primary

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

• G01K7/20

  in a specially-adapted circuit, e.g. bridge circuit · CPC title

• G01K7/026

  Arrangements for signalling failure or disconnection of thermocouples · CPC title

• G01K7/021 Primary

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