JP3254669B2 - Thermoelectric thermometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric thermometer, and more particularly, to a thermoelectric thermometer incorporating means adapted for simple calibration or automatic calibration at a place where the thermometer is used.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional thermoelectric thermometer which receives thermocouple inputs at multiple points and displays each temperature on a display. In the figure, 10 is a thermocouple, 11 is an amplifier, 12 is a switch, 21 is an A / D converter, and 22 is C
PU (microprocessor), 23 is ROM (read only memory), 24 is RAM (random access memory)
Memory), 25 is a display. 30 is an input terminal block,
Each thermocouple 10 is connected to a terminal 32 provided on a terminal block 30 directly or via a compensating wire 31. A cold junction compensation temperature sensor 33 is embedded in the terminal block 30.
Reference numeral 13 denotes a resistor, and reference numeral 14 denotes a capacitor, which constitute an RC filter for protecting a thermocouple input circuit and removing a normal mode noise.

In such a configuration, the CPU 22
The switch 12 is operated according to the program code written in the OM 23 to output the output of each thermocouple 10 to the amplifier 11.
Are sequentially supplied to the A / D converter 21 for digital conversion, and the value is stored in the RAM 24. Next, the switch 12a is operated to detect the temperature of the input terminal block 30 by the cold junction compensation temperature sensor 33, and the temperature signal is subjected to A / D conversion via the cold junction compensation circuit 40. CPU 22 is RO
A thermoelectromotive force table of each thermocouple 10 stored in M23,
The cold junction compensation calculation and the temperature conversion calculation are executed from the temperature of the input terminal block 30 and the electromotive force of each thermocouple 10, and the results are displayed on the display 25.

Conventional calibration of a thermoelectric thermometer having such a configuration is performed by the method shown in FIG. In FIG. 4, reference numeral 100 denotes FIG.
, 200 is a voltage generator for generating a stable standard voltage, and 201 is a cold junction compensation circuit incorporated in the generator 200. The generator 200 is connected to a terminal 32 provided on the thermoelectric thermometer 100 via a compensating lead 202. The terminal 32 is provided on the terminal block 30 as described with reference to FIG. 1, and each thermocouple 10 is connected to this terminal. 300 is a temperature probe,
A temperature sensor 302 is attached to the tip 301 of the probe.
Is embedded in an electrically insulated form, and this temperature sensor is connected to the cold junction compensation circuit 20 through a temperature probe 300.
1 connected. The chip 301 is fastened together with the compensating conductor 202 to the terminal 32.

In the above connection, the temperature of the terminal block 30 of the thermoelectric thermometer 100 is detected by a temperature sensor 302 provided on a temperature probe 300, and the detection output is input to a cold junction compensation circuit 201 of the voltage generator 200. .
Calibration of the thermoelectric thermometer 100 is performed by causing the voltage generator 200 to generate a voltage according to the thermoelectromotive force table from the output of the cold junction compensation circuit 201 and the set temperature in the voltage generator 200, and to generate the generated voltage as a compensating lead. This is given to the thermoelectric thermometer 100 via 202, and the measurement is performed based on the value displayed on the display 25 (shown in FIG. 3) provided in the thermoelectric thermometer.

The calibration of the thermoelectric thermometer 100 has been conventionally performed by the above-described method. However, in this method, a calibration error occurs due to the temperature probe 300 which is fastened to the terminal 32 provided on the terminal block 30. That is, when the chip 301 of the temperature probe 300 is newly fastened together with the terminal 32 of the terminal block 30, the temperature of the terminal block 30 slightly decreases due to the heat dissipation effect of the chip 301, and the temperature detected by the temperature probe 300 becomes the temperature probe. Is reduced by, for example, about 0.4 ° C. as compared with a state in which is not connected, resulting in a calibration error.
When the thermoelectric thermometer is calibrated at the place where the thermoelectric thermometer 100 is used as shown in FIG.
If the distance between 0 and the voltage generator 200 is far, the cable of the adapter 300 for cold junction compensation does not reach, and the thermometer removes all input wiring, power supply wiring, alarm contact signal wiring, etc. of the thermoelectric thermometer, and then removes the thermometer. It is necessary to remove the whole device and move it near the voltage generator 200 for calibration, which is troublesome.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. The present invention eliminates a temperature drop of a terminal block due to connection of a temperature probe to improve the accuracy of calibration and to improve the thermoelectric thermometer. It is an object of the present invention to provide a thermoelectric thermometer that can be calibrated without being affected by the distance between the thermoelectric thermometer and the standard voltage / current generator at the time of simple calibration at the place of use.

[0008]

SUMMARY OF THE INVENTION The present invention embeds a pair of temperature sensors having uniform characteristics in an input terminal block to which a thermocouple or a compensating lead is connected, and outputs the output of one of the temperature sensors to the cold junction temperature inside the instrument. It is configured so that the output of the other temperature sensor can be drawn out for calibration for use in compensation calculation.

[0009]

According to the present invention, the electric signal obtained from the calibration terminal block temperature sensor is used for the cold junction temperature compensation in the calibration instrument.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a circuit diagram showing one embodiment of a thermoelectric thermometer according to the present invention. In the figure, the same elements as those in FIG. 3 are denoted by the same reference numerals as those in FIG. In FIG.
34 is a temperature sensor, which is a temperature sensor 33
The characteristics are uniform according to the same detection principle. 41,
Reference numeral 42 denotes a connector. The sensor 34 is the sensor 3
3 is embedded in the input terminal block 30 and its output end is connected to the male part of the connector 41. 5
A switch 0 has a pair of contacts a and b, respectively.
Each contact a is connected to the protection resistor 13 of the thermocouple input circuit,
The contact b is connected to the male a of the connector 42.

FIG. 2 shows a voltage generator for calibrating the thermoelectric thermometer of FIG. In this voltage generator, 201 is a cold junction compensation circuit, 202 is a temperature setting unit, 203 is a voltage generation unit,
204 is an output amplifying unit, 205 is an input terminal, and 206 is an output terminal. The input terminal 205 is connected to the female portion b of the thermoelectric thermometer shown in FIG. 1 which is connected to the connector 41, and the output terminal 206 is connected to the female portion b of the connector 42.

When measuring the temperature with the thermoelectric thermometer shown in FIG. 1, the male a of the connectors 41 and 42 is separated from the female b of the connectors 41 and 42 of the voltage generator 200 shown in FIG. The thermometer operates as a single thermometer, and each switch 50 is connected to the contact a.
Thereby, the output of each thermocouple 10 whose cold junction temperature has been compensated as described in FIG.

Next, calibration of such a thermoelectric thermometer is shown in FIG.
In the case of using the voltage generator 200 shown in (1), the male a and the female b of the connectors 41 and 42 are connected to connect the thermoelectric thermometer and the voltage generator 200. At the same time, the changeover switch 50 is connected to the contact b. Thereby, the temperature sensor 3
An electric signal corresponding to the temperature of the input terminal block 30 detected by the input terminal 4 is applied to the cold junction compensation circuit 201 of the voltage generator 200 via the connector 41. The voltage generating circuit 203 of the voltage generator 200 generates a voltage in which the cold junction temperature accompanying the temperature of the terminal block 30 set by the temperature setting unit 202 and obtained by the cold junction temperature compensating circuit 201 is compensated. The voltage is taken out from the terminal 206 via the output amplifier 204. The voltage extracted from the terminal 206 is amplified by the amplifier 11 of the thermoelectric thermometer shown in FIG. 1 via the connector 42, converted into a digital signal by the A / D converter 21, and the value is displayed on the display 25. . The thermoelectric thermometer is calibrated based on the displayed value.

As the thermoelectric thermometer, measuring instruments and control equipment utilizing the principle of the thermoelectric thermometer, that is, a temperature controller, a digital temperature indicator, a multipoint temperature controller, a multipoint temperature monitoring device, a distributed control system , An industrial recorder, a laboratory recorder, a data recording device, a data logger, or the like.

[0015]

According to the present invention having such a configuration, at the time of calibration at the place of use, the input terminal block 3 as in the conventional apparatus is used.
Since the configuration is such that the use of the temperature probe for measuring the temperature of 0 is eliminated, it is possible to eliminate the error caused by the temperature drop of the terminal block due to the terminal connection of the temperature probe. In addition, since a temperature probe is not used, a distance between the thermoelectric thermometer and the voltage generator can be made relatively long, and a thermoelectric thermometer having such features that the calibration operation is extremely easy can be obtained. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a thermoelectric thermometer according to the present invention.

FIG. 2 is a configuration diagram showing an example of a calibration device used in the present invention.

FIG. 3 is a circuit configuration diagram of an example of a conventional thermoelectric thermometer.

FIG. 4 is a configuration diagram of an example of a calibration device used for a conventional thermoelectric thermometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermocouple 30 Input terminal board 31 Compensation conductor 33, 34 Temperature sensor

Claims (2)

(57) [Claims] A pair of temperature sensors having uniform characteristics are embedded in an input terminal block to which a thermocouple or a compensating lead wire is connected, and the output of one of the temperature sensors is used for a cold junction temperature compensation calculation inside the instrument, and the other temperature is used. A thermoelectric thermometer characterized in that a sensor output can be drawn out for calibration. 2. The output of the other temperature sensor is guided to a cold junction temperature compensation circuit of a standard voltage generator for calibration, and the cold junction temperature accompanying the temperature of the terminal block generated by the standard voltage generator for calibration is compensated. 2. The thermoelectric thermometer according to claim 1, further comprising a calibration means for calibrating the thermometer with the output voltage.