JP2010096507A - Thermocouple thermometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption in a temperature sensor output measuring circuit by reducing an operation frequency of the temperature sensor output measuring circuit included in a thermocouple thermometer, in a range not impairing the measurement accuracy. <P>SOLUTION: This thermocouple thermometer includes: a thermocouple having a temperature measuring junction, and a thermocouple output measuring circuit; a temperature sensor for detecting the temperature of a reference junction of the thermocouple, and a temperature sensor output measuring circuit; and a control part for calculating the temperature of a measuring object by an output (thermo-electromotive force) from the thermocouple and an output (reference junction temperature) from the temperature sensor at a prescribed time interval Ta. In the thermocouple thermometer, a difference between a this-time measured value and a preceding-time measured value of the thermocouple output obtained from the thermocouple output measuring circuit is determined at each prescribed time interval Ta, and an absolute value ΔA of the difference is compared with a reference value B set beforehand. Only when the absolute value ΔA is larger than the reference value B, the temperature sensor output measuring circuit is operated to measure the temperature of the reference junction, and when the absolute value ΔA is smaller than the reference value B, the temperature sensor output measuring circuit is put into an operation stop state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

 The present invention relates to a thermocouple thermometer, and more particularly to a technique for reducing power consumption in a temperature sensor output measurement circuit included in a thermocouple thermometer.

  In the thermocouple thermometer, for example, as described in Patent Document 1, one end side of two conductors made of different metals are connected to form a temperature measuring contact, and the other end side is a reference in an open state or a high impedance state. A thermocouple as a contact is used.

  When a temperature difference is applied between the temperature measuring contact and the reference contact, a thermoelectromotive force is generated between both terminals of the reference contact. Usually, the standard junction temperature is 0 ° C. Therefore, the specifications show the magnitude of the generated thermoelectromotive force as the difference between the standard junction temperature 0 ° C and the temperature measuring junction temperature. Yes.

  Therefore, when measuring the temperature of the object to be measured, it is necessary to measure the actual reference junction temperature at the measurement site and correct the thermoelectromotive force generated from the thermocouple.

  Therefore, in addition to the thermocouple and thermocouple output measurement circuit, the thermocouple thermometer is equipped with a temperature sensor that measures the reference junction temperature and a temperature sensor output measurement circuit, and the thermocouple output (thermoelectromotive force) and temperature The temperature of the object to be measured is calculated based on the output of the sensor (reference contact temperature).

Japanese Utility Model Publication No. 6-31390

  Thus, in the thermocouple thermometer, since the reference junction temperature is a factor that affects the reliability of the measurement value, conventionally, as shown in the timing chart of FIG. 4, the thermocouple output measurement and the reference junction temperature measurement are performed. Are repeatedly performed at predetermined time intervals so that highly reliable measurement values can be obtained regardless of changes in ambient temperature or the like.

  However, according to this, even when the reference junction temperature (ambient temperature) does not fluctuate, the temperature sensor output measurement circuit is put into an operating state at a predetermined time interval, so that there is a problem that power consumption increases accordingly. .

  In particular, in a thermocouple thermometer having a built-in battery as a power source, the battery life is shortened, which may lead to a situation in which measurement cannot be performed due to the battery running out during measurement.

  Accordingly, an object of the present invention is to reduce the power consumption of the temperature sensor output measurement circuit by reducing the operation frequency of the temperature sensor output measurement circuit included in the thermocouple thermometer within a range that does not impair the measurement accuracy. It is in.

  In order to solve the above-described problem, the invention described in claim 1 includes a thermocouple and a thermocouple output measuring circuit having a temperature measuring contact with respect to an object to be measured, a temperature sensor for detecting the temperature of a reference contact of the thermocouple, and A temperature sensor output measuring circuit, and a controller for calculating the temperature of the object to be measured based on the output of the thermocouple (thermoelectromotive force) and the output of the temperature sensor (reference junction temperature) at a predetermined time interval Ta. In the thermocouple thermometer including, the control unit obtains the difference between the current measurement value and the previous measurement value of the thermocouple output obtained from the thermocouple output measurement circuit at each time interval Ta, and the absolute value of the difference The value ΔA is compared with a preset reference value B, and only when the absolute value ΔA is larger than the reference value B, the temperature sensor output measurement circuit is operated to measure the temperature of the reference junction. If the absolute value ΔA is smaller than the reference value B, the temperature sensor output measurement circuit is set in an operation stop state.

  According to a second aspect of the present invention, in the first aspect, the control unit includes a memory for storing the reference junction temperature, and the latest reference junction is calculated from the memory when calculating the temperature of the object to be measured. It is characterized by reading the temperature.

  A third aspect of the present invention is characterized in that, in the second aspect, the control unit stores in the memory at least the reference junction temperature measured at the first measurement at the start of measurement.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the control unit is forced to operate when the absolute value ΔA is smaller than the reference value B for a predetermined time. In particular, the temperature sensor output measurement circuit is operated to measure the temperature of the reference junction.

  According to a fifth aspect of the present invention, in any one of the first to third aspects, the control unit forcibly operates the temperature sensor output measurement circuit at a predetermined time interval Tb longer than the time interval Ta. The temperature of the reference junction is measured.

  According to the first aspect of the invention, the difference between the current measurement value and the previous measurement value of the thermocouple output obtained from the thermocouple output measurement circuit at every predetermined time interval Ta is obtained, and the absolute value ΔA of the difference is obtained. Is compared with the preset reference value B, and only when the absolute value ΔA is larger than the reference value B, the temperature sensor output measurement circuit is operated to measure the temperature of the reference junction, and the absolute value ΔA is the reference value. When the value is smaller than the value B, the temperature sensor output measurement circuit is brought into the operation stop state, so that power consumption in the temperature sensor output measurement circuit can be reduced.

  According to the second aspect of the present invention, a memory for storing the reference junction temperature is provided, and when calculating the temperature of the object to be measured, the latest reference junction temperature is read from the memory, so that the predetermined time interval Ta is obtained. The temperature of the object to be measured can be calculated based on the thermocouple output measured in step (b) and the latest reference junction temperature read from the memory.

  According to the invention described in claim 3, the absolute value ΔA is smaller than the reference value B from the start of measurement by storing in the memory at least the reference junction temperature measured at the first measurement at the start of measurement. Even if it continues, the temperature of the object to be measured can be calculated.

  According to the fourth aspect of the present invention, when the absolute value ΔA is smaller than the reference value B is continued for a predetermined time, the temperature sensor output measurement circuit is forcibly operated to measure the temperature of the reference contact. By doing so, the reliability of the measured value (temperature of the object to be measured) is ensured.

  According to the fifth aspect of the present invention, the temperature of the reference contact is measured by forcibly operating the temperature sensor output measurement circuit at a predetermined time interval Tb longer than the predetermined time interval Ta. As in the invention according to claim 4, the reliability of the measured value (temperature of the object to be measured) is ensured.

  Next, the best embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the configuration of a thermocouple thermometer according to the present invention, FIG. 2 is a flowchart for explaining the operation of a control unit, and FIG. It is a timing chart.

  As shown in FIG. 1, this thermocouple thermometer has, as a basic configuration, a thermocouple 10 as a temperature sensor for an object to be measured (not shown), and a measuring device main body 20 to which the thermocouple 10 is connected. Prepare.

  The thermocouple 10 includes two conductors 10a and 10b made of dissimilar metals, one end of which is connected to each other as a temperature measuring contact 11 for the object to be measured, and the other ends 12a and 12b are open or high. It is connected to the measuring instrument main body 20 as an impedance reference contact 12. In the present invention, any of B, R, S, K, E, J, and T may be used for the thermocouple 10.

  A reference junction 12 is connected to the inside of the measuring instrument body 20 and is arranged in the vicinity of the reference junction 12 and a thermocouple output measurement circuit 21 for measuring the output (thermoelectromotive force) of the thermocouple 10. , A temperature sensor output measuring circuit 23 for measuring the output (reference contact temperature) of the temperature sensor 22, a control unit 24, a display unit 25, a memory 26, and a communication unit 27. ing.

  For the control unit 24, for example, a CPU or a microcomputer having an arithmetic processing function may be used. The control unit 24 uses the thermocouple output (thermoelectromotive force) output from the thermocouple output measurement circuit 21 and the reference junction temperature output from the temperature sensor output measurement circuit 23 according to a standard method to determine the object to be measured. Calculate the temperature.

  As the display unit 25, a display panel made of liquid crystal or plasma can be used. In some cases, a printer may be used. The memory 26 includes a ROM that stores an operation program for the control unit 24 and a work RAM for work. The communication unit 27 is an interface for communicating with an external device such as a personal computer.

  Next, the operation of the present invention will be described with reference to FIGS. In general, the present invention is such that since the amount of fluctuation of the temperature of the reference junction 12 is moderate with respect to the measured value of the thermocouple 10, the reference value can be obtained only when the measured value of the thermocouple 10 fluctuates beyond a predetermined value. Basically, the temperature of the contact 12 is measured.

  First, when a measurement start button (not shown) is turned on, the control unit operates the thermocouple output measurement circuit 21 at a predetermined time interval Ta (t1, t2, t3,... However, if it is the first measurement after the start of measurement in step ST10, steps ST11 to ST13 are executed.

  That is, at the time of the first measurement, after the thermocouple output measurement circuit 21 is operated and the thermocouple output V is acquired in step ST11, the temperature sensor output measurement circuit 23 is operated and the reference junction temperature S is acquired in step ST12. . The thermocouple output V and the reference junction temperature S are taken in as voltage data via an A / D converter (not shown).

  In step ST13, the temperature of the measurement object (not shown) is calculated from the thermocouple output V and the reference junction temperature S, and the calculated temperature value is displayed on the display unit 25, and the reference junction temperature S is stored in the memory 26. To do.

  Then, after waiting for the time Ta to elapse in step ST14 (after waiting for an interval), if the measurement is not stopped in step ST15, the process returns to step ST10, and steps ST16 to ST19 are executed after the second measurement. .

  That is, in step ST16, the thermocouple output measuring circuit 21 is operated to take in the thermocouple output V. The thermocouple output V is the current measurement value V2, the thermocouple output V captured in the previous first time is the previous measurement value V1, and the difference (V2−V1) between the current measurement value V2 and the previous measurement value V1 in step ST17. ) Is calculated. The absolute value | V2−V1 | is ΔA.

  If the thermocouple output at the n-th measurement is Vn and the preceding n-1th thermocouple output is Vn-1, the difference of (Vn)-(Vn-1) is calculated in step ST17. The

  In the control unit 24, a reference value B for the absolute value ΔA is set in advance, and it is determined in step ST18 whether ΔA> B. If NO, that is, if the absolute value ΔA is smaller than the reference value B, it is determined that the reference junction temperature S has not fluctuated, and step ST13 is executed without measuring the reference junction temperature.

  In step ST13, the temperature of the object to be measured is calculated from the thermocouple output V and the reference junction temperature S. In this case, the reference junction temperature S is read from the memory 26.

  On the other hand, if the determination in step ST18 is YES, that is, if the absolute value ΔA is larger than the reference value B, it is determined that the reference junction temperature S is fluctuating, and in step ST19, the temperature sensor output measurement circuit is determined. 23 is operated to take in the reference junction temperature Snew.

  In step ST13, the temperature of the object to be measured is calculated from the newly acquired reference junction temperature Snew and the thermocouple output V2 acquired in step ST16, and the calculated temperature value is displayed on the display unit 25. The contact temperature Snew is stored in the memory 26, and preferably the reference contact temperature S is rewritten to Snew.

  Thereafter, similarly, steps ST16 to 19 and ST13 to 15 are repeatedly executed until a measurement stop command is issued. However, when step ST19 is not performed, the latest reference junction temperature Snew is read from the memory 26, Calculate the temperature of the object to be measured.

  FIG. 3 schematically shows an example of the transition of the thermocouple output V. As can be seen from this, in this example, the reference junction temperature is measured only during the measurement of t4, t5, t11, t12, and t13 where the thermocouple output V fluctuates greatly, and the other thermocouple outputs V are relatively low. Since the reference junction temperature is not measured when it is stable, the power consumption is reduced accordingly.

  However, since the temperature of the thermocouple and the reference junction may fluctuate similarly, when the absolute value ΔA is smaller than the reference value B is continued for a predetermined time, the temperature sensor output measurement circuit is forcibly 23 is preferably operated to measure the temperature of the reference junction.

  As another method, the temperature of the reference junction may be measured by forcibly operating the temperature sensor output measurement circuit 23 at a predetermined time interval Tb longer than the time interval Ta.

The schematic diagram which shows the structure of the thermocouple thermometer of this invention. The flowchart for operation | movement description of a control part. The timing chart for demonstrating the relationship between transition of a thermocouple output, and a reference junction temperature measurement. The timing chart which shows the thermocouple output measurement and the reference junction temperature measurement which were conventionally performed as a pair.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Thermocouple 11 Temperature measuring contact 12 Reference contact 20 Measuring device main body 21 Thermocouple output measuring circuit 22 Temperature sensor 23 Temperature sensor output measuring circuit 24 Control part 25 Display part 26 Memory 27 Communication part

Claims (5)

A thermocouple having a temperature measuring contact with respect to the object to be measured and a thermocouple output measuring circuit, a temperature sensor for detecting the temperature of the reference junction of the thermocouple, a temperature sensor output measuring circuit, and the thermocouple at a predetermined time interval Ta A thermocouple thermometer including a control unit that calculates the temperature of the object to be measured by the output of the sensor (thermoelectromotive force) and the output of the temperature sensor (reference contact temperature),
The control unit obtains a difference between the current measurement value and the previous measurement value of the thermocouple output obtained from the thermocouple output measurement circuit at each time interval Ta, and the absolute value ΔA of the difference is preset. Only when the absolute value ΔA is larger than the reference value B, the temperature sensor output measuring circuit is operated to measure the temperature of the reference contact, and the absolute value ΔA is The thermocouple thermometer characterized in that when it is smaller than the reference value B, the temperature sensor output measurement circuit is stopped.   The said control part is provided with the memory which preserve | saves the said reference junction temperature, When calculating the temperature of the said to-be-measured object, the said latest reference junction temperature is read from the said memory, The said reference part is characterized by the above-mentioned. Thermocouple thermometer.   3. The thermocouple thermometer according to claim 2, wherein the control unit stores at least the reference junction temperature measured at the first measurement at the start of measurement in the memory.   When the absolute value ΔA is smaller than the reference value B continues for a predetermined time, the control unit forcibly operates the temperature sensor output measurement circuit to measure the temperature of the reference contact. The thermocouple thermometer according to any one of claims 1 to 3.   4. The controller according to claim 1, wherein the control unit forcibly operates the temperature sensor output measurement circuit at a predetermined time interval Tb longer than the time interval Ta to measure the temperature of the reference junction. The thermocouple thermometer according to claim 1.

Images