KR20080090005A - A temperature measuring apparatus using a thermocouple and a method thereof - Google Patents

A temperature measuring apparatus using a thermocouple and a method thereof Download PDF

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Publication number
KR20080090005A
KR20080090005A KR1020070032923A KR20070032923A KR20080090005A KR 20080090005 A KR20080090005 A KR 20080090005A KR 1020070032923 A KR1020070032923 A KR 1020070032923A KR 20070032923 A KR20070032923 A KR 20070032923A KR 20080090005 A KR20080090005 A KR 20080090005A
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KR
South Korea
Prior art keywords
temperature
analog
thermocouple
digital converter
signal
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Application number
KR1020070032923A
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Korean (ko)
Inventor
신용각
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엘에스산전 주식회사
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Priority to KR1020070032923A priority Critical patent/KR20080090005A/en
Publication of KR20080090005A publication Critical patent/KR20080090005A/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
    • G01K7/10—Arrangements for compensating for auxiliary variables, e.g. length of lead
    • G01K7/12—Arrangements with respect to the cold junction, e.g. preventing influence of temperature of surrounding air
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/02—Means for indicating or recording specially adapted for thermometers
    • G01K1/026—Means for indicating or recording specially adapted for thermometers arrangements for monitoring a plurality of temperatures, e.g. by multiplexing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/20—Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K15/00—Testing or calibrating of thermometers
    • G01K15/005—Calibration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
    • G01K7/10—Arrangements for compensating for auxiliary variables, e.g. length of lead
    • G01K7/12—Arrangements with respect to the cold junction, e.g. preventing influence of temperature of surrounding air
    • G01K7/13—Circuits for cold-junction compensation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K2219/00—Thermometers with dedicated analog to digital converters

Abstract

A temperature measuring apparatus using a thermocouple and a method thereof are provided to remove a temperature drift of a compensation circuit by using an accurate reference resistance. A temperature measuring apparatus comprises a thermocouple(102), an analog digital converter(105), and a cold junction compensator. The thermocouple outputs an analog thermometric voltage signal as a voltage signal by converting the temperature of an object(101). The analog digital converter connected to an output end of the thermocouple outputs the analog thermometric voltage signal into a digital signal. The cold junction compensator provides the ambient temperature of the thermocouple as an analog compensation voltage signal to the analog digital converter. The analog digital converter includes an accurate reference resistance and a processor(106). The accurate reference resistance is connected to the cold junction compensator in series to provide a reference voltage for canceling the drift effect according to the temperature of the cold junction compensator. The processor, connected to the output end of the analog digital converter, determines the temperature of the object based on the thermometric voltage signal and the compensation voltage signal.

Description

Thermometer using thermocouple and method thereof {A TEMPERATURE MEASURING APPARATUS USING A THERMOCOUPLE AND A METHOD THEREOF}

1 is a block diagram showing the configuration of a temperature measuring apparatus using a thermocouple according to the present invention;

2 is a flowchart illustrating a temperature measuring method using a thermocouple according to the present invention.

* Explanation of symbols on the main parts of the drawings

101: temperature measurement object 102: thermocouple

103: cold junction compensator 104: reference resistance

105: analog-to-digital converter 105a: constant current source

105b: multiplexer 105c: instrumentation amplifier

105d: sigma delta analog to digital converter

106: microprocessor

The present invention relates to a temperature measuring apparatus and method using a thermocouple.

Thermocouplers using thermocouples have been fabricated by adding compensation circuits to compensate for the effects of undesired ambient temperatures. The compensation circuit is implemented by adding a reference voltage generator circuit to an input terminal and a method of adding a temperature sensor and a multiplexer. In particular, the method using a temperature sensor and a multiplexer reduces the complexity and error of the method of adding a reference voltage generator circuit. It is a method designed to reduce.

In the temperature measuring device using the temperature sensor and the multiplexer, when a temperature change occurs at the installation place of the temperature measuring device, there is a problem that an error occurs in the temperature measurement due to the temperature drift.

In addition, in the temperature measuring device using a temperature sensor and a multiplexer according to the prior art, the signal amplification unit and the multiplexer is configured independently of the front circuit of the analog-to-digital converter, so that the overall size of the temperature measuring device increases and the manufacturing cost increases. have.

Accordingly, the present invention is to solve the problems of the prior art, the temperature measuring device using a thermocouple capable of offsetting the temperature drift that the compensation circuit has, miniaturization of the temperature measuring device can be implemented at a low manufacturing cost and its It is an object to provide a method.

An object of the present invention, the thermocouple for converting the temperature of the temperature measurement object into thermoelectric power, and outputs an analog temperature measurement voltage signal as a voltage signal;

An analog-to-digital converter connected to an output terminal of the thermocouple and converting an analog RTD signal from the thermocouple into a digital signal and outputting the digital signal;

A cold junction compensator connected to the analog-to-digital converter, for measuring the ambient temperature of the thermocouple and converting the analog-to-digital converter into an analog compensation voltage signal, wherein the analog-digital converter converts the analog compensation voltage signal into a digital compensation voltage. Convert to a signal;

A precision reference resistor connected in series with the cold junction compensator to provide a reference voltage that cancels the drift effect with temperature of the cold junction compensator;

Connected to an output terminal of the analog-to-digital converter, based on the temperature measurement voltage signal measured by the thermocouple converted into a digital signal by the analog-digital converter, and the compensation voltage signal measured by the cold junction compensator. It can be achieved by providing a temperature measuring device using a thermocouple according to the invention, characterized in that it comprises a processor;

The object of the present invention, in the method for measuring the temperature using a thermocouple,

Obtaining a temperature measurement voltage value by converting the temperature of the temperature measuring object into thermoelectric power using a thermocouple;

Compensation voltage according to the ambient temperature of the thermocouple of the cold junction compensator

Obtaining by using a voltage change according to an ambient temperature;

Canceling a temperature drift of the cold junction compensator using a precision reference resistor connected in series with the cold junction compensator;

Converting by using a processor to a predetermined ambient temperature in preparation for the compensation voltage;

Converting the converted ambient temperature into a voltage using a processor according to a predetermined thermoelectric-to-temperature conversion table;

Adding a value obtained by converting the ambient temperature into a voltage using a temperature conversion table based on a predetermined thermoelectric power to the measured temperature value obtained in the step of obtaining the measured temperature voltage value; And

Converting the value converted into the voltage into a temperature based on a temperature conversion table with respect to the standard voltage to finally determine the temperature of the temperature measuring object; using the thermocouple according to the present invention By providing a method of measuring temperature.

The object of the present invention and the configuration and effect of the present invention to achieve the same will be more clearly understood by the following description of the preferred embodiment of the present invention with reference to the accompanying drawings.

First, referring to FIG. 1, which shows a block diagram of a temperature measuring apparatus using a thermocouple according to the present invention, is as follows.

The temperature measuring device using the thermocouple according to the present invention includes a thermocouple 102, an analog-digital converter 105, a cold junction compensator 103, a precision reference resistor 104, and a microprocessor 106. It is configured to include.

Reference numeral 101 denotes a temperature measuring object that is an object to be measured for temperature, and the thermocouple 102 converts the temperature of the temperature measuring object 101 into thermoelectric power, and outputs an analog temperature measuring voltage signal V TC as a voltage signal. .

Analog-to-digital converter 105 is connected to the output terminal of the thermocouple 102, its first analog input terminal (AIN1 +, AIN1-), converts the analogue temperature measurement voltage signal (V TC ) from the thermocouple 102 into a digital signal and outputs it. do.

The analog-to-digital converter 105 inputs the temperature measurement voltage signal V TC from the thermocouple 102, the input of the analog compensation voltage signal from the cold junction compensator 103, and the precision reference resistor 104. It consists of a multichannel analog-to-digital converter with a multichannel input to receive a reference voltage input.

The cold junction compensator 103 is connected to the second analog input terminals AIN2 + and AIN2- of the analog-to-digital converter 105 to measure the ambient temperature of the thermocouple 102 to the analog-to-digital converter 105 to measure the analog compensation voltage signal. Provided by converting. Then, the analog-to-digital converter 105 converts the analog compensation voltage signal into a digital compensation voltage signal and outputs it.

The precision reference resistor 104 is connected in series to the cold junction compensator 103, so that the reference voltage for canceling the drift effect according to the temperature of the cold junction compensator 103 may be applied. It is provided to the reference voltage input terminal {REFIN (+), REFIN (-)}. More specifically, since the precision reference resistor 104 is a means for generating and providing a reference voltage of the analog-to-digital converter 105, a resistor whose resistance is precisely measured is used. With respect to the temperature drift characteristic of the cold junction compensator 103, i.e., the resistance varies with temperature, the precision reference resistor 104 is connected in series with the cold junction compensator 103 to a constant current source and is connected to the temperature. As a result of the drift, the drift effect according to the temperature of the cold junction compensator 103 is canceled.

The microprocessor 106 may be replaced with a processor capable of calculating and processing input values according to other programs such as a personal computer, and is connected to an output terminal of the analog-digital converter 105. The microprocessor 106 is based on the temperature measurement voltage signal V TC measured by the thermocouple 102 converted into a digital signal by the analog-digital converter 105 and the compensation voltage signal measured by the cold junction compensator 103. The temperature of the body temperature target object 101 is calculated and determined.

The analog-to-digital converter 105 includes a constant current source 105a, a multiplexer 105b, a measurement amplifier 105c, and an analog-to-digital converter 105d therein. That is, the analog-to-digital converter 105 is a one chip having the functions of a constant current source 105a, a multiplexer 105b, a measurement amplifier 105c, and an analog-digital converter 105d. ) Circuit, so that the circuit can be simplified, the size can be downsized, and the manufacturing cost is also low.

The constant current source 105a is connected to the cold junction compensator 103 and the precision reference resistor 104 through the rectifying output stage IOUT to supply a constant current to them. Therefore, the voltage characteristics according to the temperature of the cold junction compensator 103 and the precision reference resistor 104 connected to each other in series by a common constant current supplied from the constant current source 105a are dripped together with the change of the ambient temperature. It can be offset.

The multiplexer 105b sequentially selects and outputs the analog RTD signal V TC from the thermocouple 102 and the analog compensation voltage signal from the cold junction compensator 103 one by one.

The measuring amplifier 105c is connected to the output terminal of the multiplexer 105b, and amplifies and outputs the analog temperature measurement voltage signal V TC or the analog compensation voltage signal output by the multiplexer 105b. Since the voltage signal generated by the thermoelectric power is generally a fine signal of 100 mV (millivolts) or less, it is necessary to amplify the fine signal.

The analog-to-digital converter 105d is connected to the output terminal of the measurement amplifier 105c, and converts the amplified analog temperature measurement voltage signal V TC or the analog compensation voltage signal output by the measurement amplifier 105c into a digital signal. To print.

The analog-to-digital converter 105d is preferably configured as a sigma delta analog digital converter that converts an analog signal into a digital signal at high speed accurately and has a strong characteristic of noise.

On the other hand, it will be described with reference to Figures 2 and 1 showing the temperature measurement method using a thermocouple according to the present invention and the operation of the temperature measuring device as a flow chart as follows.

2, first, in step 201, the temperature of the temperature measuring object (see reference numeral 101 in FIG. 1) is converted into thermoelectric power using a thermocouple (symbol 102 in FIG. 1) to measure the measured temperature voltage value, that is, the measured temperature voltage signal. (V TC ) is obtained.

In a next step 202, the microprocessor 106 of FIG. 1 is used to store the RTD value, ie, the RTC signal V TC .

In the next step 203, the cold junction compensator 103 detects the compensation voltage according to the ambient temperature, amplifies it using the measuring amplifier 105c and converts it into a digital value using the analog-to-digital converter 105d. To the microprocessor 106.

The step 203 is a step of obtaining the compensation voltage according to the ambient temperature of the thermocouple 102 using the voltage change according to the ambient temperature of the cold junction compensator 103, and is connected in series to the cold junction compensator 103 Using the precision reference resistor 104, the step of offsetting the temperature drift of the cold junction compensator 103 is included as a detail step.

Next, the compensation voltage detected by the cold junction compensator 103 in step 204 is converted into a digital value using the analog-to-digital converter 105d and stored by the microprocessor 106.

Next, in step 205, the microprocessor 106 is converted to a predetermined ambient temperature in preparation for the compensation voltage.

Next, the ambient temperature converted in step 206 is converted into a voltage using the microprocessor 106 as a voltage by a predetermined thermoelectric-to-temperature conversion table (not shown).

Next, in step 207, a temperature conversion table in the microprocessor 106 is compared to thermal electromotive force predetermined for the ambient temperature of the temperature detecting voltage value (V TC) obtained in the step 201 of obtaining the temperature detecting voltage value (V TC) The value converted into voltage is added.

Next, in steps 208 and 209, the microprocessor 106 converts the value converted into the voltage into a temperature based on a temperature conversion table with respect to a predetermined standard voltage to finally determine the temperature of the temperature measuring object. That is, if the microprocessor 106 determines the temperature of the object to be measured in step 208 in terms of different representations, for example, in degrees Celsius (° C.) in step 208, for example, in step 209 Determined in (F).

According to the present invention, there is provided a temperature measuring apparatus and method using a thermocouple capable of canceling the temperature drift that the compensation circuit has as described above, miniaturizing the temperature measuring apparatus, and realizing a low manufacturing cost. There is an effect that can be obtained.

Claims (5)

A thermocouple converting the temperature of the temperature measuring object into thermoelectric power and outputting an analog temperature measurement voltage signal as a voltage signal; An analog-to-digital converter connected to an output terminal of the thermocouple and converting an analog RTD signal from the thermocouple into a digital signal and outputting the digital signal; A cold junction compensator connected to the analog-to-digital converter, for measuring the ambient temperature of the thermocouple and converting the analog-to-digital converter into an analog compensation voltage signal, wherein the analog-digital converter converts the analog compensation voltage signal into a digital compensation voltage. Convert to a signal; A precision reference resistor connected in series with the cold junction compensator to provide a reference voltage that cancels the drift effect with temperature of the cold junction compensator; Connected to an output terminal of the analog-to-digital converter, based on the temperature measurement voltage signal measured by the thermocouple converted into a digital signal by the analog-digital converter, and the compensation voltage signal measured by the cold junction compensator. And a processor that calculates and determines a temperature. The method of claim 1, The analog to digital converter, A constant current source for supplying a constant current to the cold junction compensator and the precision reference resistor; A multiplexer for selecting and outputting the analog RTD signal from the thermocouple and the analog compensation voltage signal from the cold junction compensator one by one; A measurement amplifier connected to an output terminal of the multiplexer and amplifying and outputting an analog temperature measurement voltage signal or the analog compensation voltage signal output by the multiplexer; And an analog-digital converter connected to an output terminal of the measuring amplifier and converting the amplified analogue temperature measurement voltage signal or the analog compensation voltage signal output by the measuring amplifier into a digital signal and outputting the converted digital signal. Temperature measuring device using a thermocouple. The method of claim 2, The analog-to-digital converter is a sigma delta analog-to-digital converter that converts an analog signal into a digital signal at high speed accurately and resistant to noise. The method of claim 1, The analog-to-digital converter has a multichannel input for receiving an input of a temperature measurement voltage signal from the thermocouple, an input of an analog compensation voltage signal from the cold junction compensator, and a reference voltage from the precision reference resistor. Temperature measuring device using a thermocouple, characterized in that composed of a channel analog to digital converter. In the method of measuring the temperature using a thermocouple, Obtaining a temperature measurement voltage value by converting the temperature of the temperature measuring object into thermoelectric power using a thermocouple; Compensation voltage according to the ambient temperature of the thermocouple of the cold junction compensator Obtaining by using a voltage change according to an ambient temperature; Canceling a temperature drift of the cold junction compensator using a precision reference resistor connected in series with the cold junction compensator; Converting by using a processor to a predetermined ambient temperature in preparation for the compensation voltage; Converting the converted ambient temperature into a voltage using a processor according to a predetermined thermoelectric-to-temperature conversion table; Adding a value obtained by converting the ambient temperature into a voltage using a temperature conversion table based on a predetermined thermoelectric power to the measured temperature value obtained in the step of obtaining the measured temperature voltage value; And Determining the temperature of the temperature measurement target by converting the value converted into the voltage into a temperature based on a temperature conversion table with respect to the standard voltage; Way.
KR1020070032923A 2007-04-03 2007-04-03 A temperature measuring apparatus using a thermocouple and a method thereof KR20080090005A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101323874B1 (en) * 2011-07-20 2013-10-30 엘에스산전 주식회사 A compact temperature thermocouple module and a plc equipped therewith
CN105334384A (en) * 2015-10-22 2016-02-17 宁波三星医疗电气股份有限公司 Method for selecting sampling resistor for three phase meter
CN105466460A (en) * 2015-12-18 2016-04-06 深圳市贝沃德克生物技术研究院有限公司 Circuit temperature drift compensation system and method of biosensor
EP3109607A3 (en) * 2015-06-24 2017-01-04 LSIS Co., Ltd. Method for temperature drift compensation of temperature measurement device using thermocouple
CN112763086A (en) * 2020-12-26 2021-05-07 广东电网有限责任公司电力科学研究院 Temperature measurement compensating system and temperature measurement compensating device

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101323874B1 (en) * 2011-07-20 2013-10-30 엘에스산전 주식회사 A compact temperature thermocouple module and a plc equipped therewith
EP3109607A3 (en) * 2015-06-24 2017-01-04 LSIS Co., Ltd. Method for temperature drift compensation of temperature measurement device using thermocouple
CN106289559A (en) * 2015-06-24 2017-01-04 Ls产电株式会社 For the method using the temperature drift compensation of the temperature measuring equipment of thermocouple
JP2017009611A (en) * 2015-06-24 2017-01-12 エルエス産電株式会社Lsis Co., Ltd. Method for temperature drift compensation of temperature measurement device using thermocouple
US10101217B2 (en) 2015-06-24 2018-10-16 Lsis Co., Ltd. Method for temperature drift compensation of temperature measurement device using thermocouple
CN105334384A (en) * 2015-10-22 2016-02-17 宁波三星医疗电气股份有限公司 Method for selecting sampling resistor for three phase meter
CN105466460A (en) * 2015-12-18 2016-04-06 深圳市贝沃德克生物技术研究院有限公司 Circuit temperature drift compensation system and method of biosensor
WO2017101549A1 (en) * 2015-12-18 2017-06-22 深圳市贝沃德克生物技术研究院有限公司 Biosensor circuit temperature drift compensation system and method
CN105466460B (en) * 2015-12-18 2019-08-30 深圳市贝沃德克生物技术研究院有限公司 The circuit temperature drift compensating system and method for biosensor
CN112763086A (en) * 2020-12-26 2021-05-07 广东电网有限责任公司电力科学研究院 Temperature measurement compensating system and temperature measurement compensating device

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