JPH08233665A - Thermoelectric thermometer - Google Patents

Abstract

PURPOSE: To enhance calibrating accuracy by embedding a pair of temperature sensors uniform in a characteristic in an input terminal stand to which a thermocouple is connected, and constituting so that one temperature sensor output is pulled outside for cold junction temperature compensating operation and the other for calibration. CONSTITUTION: When a thermometer is calibrated, a male (a) and a female (b) of connectors 41 and 42 are joined together, and a thermoelectric thermometer and a voltage generator 200 are connected to each other, and a switch 50 is connected to the connecting B side. Therefore, an electric signal corresponding to a temperature of an input terminal stand 30 detected by a temperature sensor 33 is added to a cold junction temperature compensating circuit 201 of the generator 200 through the connector 41. Voltage is generated in a voltage generating circuit 203 since a cold junction temperature caused by a temperature of the terminal stand 30 obtained by the circuit 201 set by a temperature setting part 202 is compensated. The generated voltage is taken out of a terminal 206 through an output amplifier 204. The taken-out voltage is amplified, and is converted by an A/D converter 21, and is displayed by a display unit 25.

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 a plurality of thermocouple inputs 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 ROM (read only memory), 24 RAM (random access memory)
Memory) and 25 are indicators. 30 is an input terminal block,
Each thermocouple 10 is connected to a terminal 32 provided on the terminal block 30 directly or via a compensation lead wire 31. A cold junction compensation temperature sensor 33 is embedded in the terminal block 30.
Reference numeral 13 is a resistor, and 14 is a capacitor, which constitute an RC filter for protecting the thermocouple input circuit and removing normal mode noise.

In such a configuration, the CPU 22 has the R
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
Is sequentially given to the A / D converter 21 via the 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 AD-converted via the cold junction compensation circuit 40. CPU22 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 unit 25.

The conventional calibration of the thermoelectric thermometer having such a configuration is performed by the method shown in FIG. In FIG. 4, 100 is the same as in FIG.
2 is a thermoelectric thermometer, 200 is a voltage generator that generates a stable standard voltage, and 201 is a cold junction compensation circuit incorporated in the generator 200. The generator 200 is connected to the terminal 32 provided on the thermoelectric thermometer 100 via a compensation lead wire 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 this probe.
Is embedded in an electrically insulated form, and this temperature sensor is equipped with a cold junction compensation circuit 20 via a temperature probe 300.
Connected to 1. The tip 301 is fastened together with the compensation lead wire 202 to the terminal 32.

In the above connection, the temperature of the terminal block 30 of the thermoelectric thermometer 100 is detected by the temperature sensor 302 provided in the temperature probe 300, and the detection output is input to the cold junction compensation circuit 201 in the voltage generator 200. .
The thermoelectric thermometer 100 is calibrated 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 in the voltage generator 200 and the set temperature, and compensating the generated voltage. It is given to the thermoelectric thermometer 100 via 202, and is performed by the value displayed on the display 25 (shown in FIG. 3) provided on the thermoelectric thermometer.

The thermoelectric thermometer 100 has been conventionally calibrated by the above-mentioned method. However, this method causes a calibration error caused by the temperature probe 300 that is fastened together with the terminal 32 provided on the terminal block 30. That is, when the chip 301 of the temperature probe 300 is newly fastened to the terminal 32 of the terminal block 30, the temperature of the terminal block 30 is slightly lowered due to the heat dissipation effect of the chip 301, and the temperature detected by the temperature probe 300 is the temperature probe. As compared with the state in which is not connected, for example, it decreases by about 0.4 ° C, and as a result, a calibration error occurs.
When the thermoelectric thermometer 100 is calibrated as shown in FIG. 2 at the place of use, the thermoelectric thermometer 10
When 0 is separated from the voltage generator 200, the cable of the adapter 300 for cold junction compensation does not reach, and the thermometer thermometer input wiring, power supply wiring, alarm contact signal wiring, etc. are all removed before the thermometer. Since it is necessary to remove the whole and move it near the voltage generator 200 for calibration, it is troublesome.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it eliminates the temperature drop of the terminal block due to the connection of the temperature probe to improve the accuracy of calibration and 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 during simple calibration at the place of use.

[0008]

According to the present invention, 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 one temperature sensor output is used as a cold junction temperature inside a meter. It is configured to be used for compensation calculation and to be able to draw the output of the other temperature sensor to the outside for calibration.

[0009]

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

[0010]

The present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an embodiment of a thermoelectric thermometer according to the present invention. In the figure, the same elements as those in FIG. 3 are assigned the same reference numerals as those in FIG. 3 and their re-explanation is omitted. In FIG.
34 is a temperature sensor, and this temperature sensor is the temperature sensor 33.
It has the same characteristics based on the same detection principle. 41,
42 are connectors respectively. The sensor 34 is the sensor 3
It is embedded in the input terminal block 30 in the vicinity of 3, and its output end is connected to the male part a of the connector 41. 5
0 is a changeover switch having a pair of contacts a and b,
Each contact a is connected to the protection resistor 13 of the thermocouple input circuit,
The contact b is connected to the male part 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 generating unit,
Reference numeral 204 is an output amplifier, 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 the temperature is measured by 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 thermometer alone, and each changeover switch 50 is connected to the contact a side.
As a result, the output of each thermocouple 10 in which the cold junction temperature is compensated as described in FIG. 1 is displayed on the display 25.

Next, the calibration of such a thermoelectric thermometer is shown in FIG.
In the case of using the voltage generator 200 shown in (1), the thermoelectric thermometer and the voltage generator 200 are connected by connecting the male a and female b of the connectors 41 and 42. At the same time, the changeover switch 50 is connected to the contact b side. As a result, the temperature sensor 3
An electrical signal corresponding to the temperature of the input terminal block 30 detected by 4 is applied to the cold junction compensation circuit 201 of the voltage generator 200 via the connector 41. In the voltage generation circuit 203 of the voltage generator 200, a voltage in which the cold junction temperature due to the temperature of the terminal block 30 set by the temperature setting unit 202 and obtained by the cold junction temperature compensation circuit 201 is compensated is generated, and this generated voltage is generated. The voltage is taken out from the terminal 206 via the output amplifier 204. The voltage extracted from the terminal 206 is amplified via the connector 42 by the amplifier 11 of the thermoelectric thermometer shown in FIG. 1, 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 this displayed value.

As the thermoelectric thermometer, a measuring instrument / control device utilizing the principle of the thermoelectric thermometer, that is, a temperature controller, a digital temperature indicator, a multipoint temperature control device, a multipoint temperature monitoring device, a distributed control system. It may be 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 structure, the input terminal block 3 like the conventional device is used at the time of calibration at the place of use.
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 due to the temperature drop of the terminal block due to the terminal connection of the temperature probe. Further, since the temperature probe is not used, the distance between the thermoelectric thermometer and the voltage generator can be made relatively long, and the calibration operation thereof is extremely easy to obtain. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a circuit configuration 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 block diagram of an example of a calibration device used in a conventional thermoelectric thermometer.

[Explanation of symbols]

 10 Thermocouple 30 Input Terminal Board 31 Compensation Lead Wire 33, 34 Temperature Sensor

Claims (2)

[Claims] 1. A pair of temperature sensors with 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 temperature sensor is used for cold junction temperature compensation calculation inside the instrument, while the other temperature is used. A thermoelectric thermometer characterized in that the sensor output is configured to be drawn to the outside for calibration. 2. The output of the other temperature sensor is led to a cold junction temperature compensating circuit of a calibration standard voltage generator, and the cold junction temperature due to the temperature of the terminal block generated by the calibration standard voltage generator is compensated. The thermoelectric thermometer according to claim 1, further comprising a calibration means for calibrating the thermometer with the voltage output.