JPH06207862A - Receiving instrument connected with thermocouple - Google Patents

Abstract

PURPOSE:To enable reduction of the number of temperature sensors for reference junction compensation to be installed actually, by providing an arithmetic means for calculating each reference junction compensation voltage on the basis of the reference junction compensation voltage outputted from an output part of a reference junction compensation means. CONSTITUTION:Adders 11 to 15 add reference junction compensation voltages based on temperatures of reference junction spots to thermoelectromotive forces of thermocouples 1 to 5. Reference junction compensation means 22 and 24 correspond to thermocouples 2 and 4 and comprise temperature sensors 32 and 34 and output parts 42 and 44 outputting reference junction compensation voltages based on temperature signals of the sensors, respectively. An arithmetic means 10 calculates reference junction compensation voltages for compensation relating to reference junction temperatures on the basis of the reference junction compensation voltages outputted from the means 22 and 24, for outputs of the thermocouples 1, 3 and 5 other than the thermocouples 2 and 4. In other words, the means 22 and 24 and, accordingly, the sensors 32 and 34 for reference junctions correspond only to two out of five thermocouples in all and the reference junction compensation voltages corresponding to the three remainders are outputted by the means 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving instrument in which a plurality of thermocouples are connected via compensating conductors and cold junction compensation is performed for each of the thermocouples. The present invention relates to a thermocouple-connected receiver instrument in which the number of actual installations is reduced to reduce costs.

[0002]

2. Description of the Related Art Each conventional method will be described with reference to FIG. FIG. 4 shows a method related to thermocouple connection,
(a) is a schematic diagram of the direct method, (b) is a schematic diagram of the copper conductor method,
(c) is a schematic diagram of the compensating lead wire system. In Figure 4 (a), the cold junction side of the thermocouple is directly connected to the receiving instrument. Since the thermoelectromotive force of this thermocouple is determined by the difference between the temperature Th of the temperature measuring junction and the temperature Tc of the cold junction, the accurate temperature Th can be obtained by compensating for the cold junction temperature, that is, depending on the cold junction temperature. It is necessary to add the generated thermoelectromotive force to the thermoelectromotive force of the thermocouple. Therefore, although not shown here, a temperature sensor is attached to the cold junction portion (connection portion of the thermocouple to the receiving instrument), and the compensation voltage based on the temperature signal is added to the thermocouple electromotive force. In FIG. 4 (b), the thermocouple is connected to the receiving instrument via a copper wire connected to its cold junction side. If the temperature of the cold junction (connection point between the thermocouple and the copper conductor) is maintained at the reference cold junction temperature of 0 ° C, the thermoelectromotive force of this thermocouple will accurately indicate the measured temperature. . In FIG. 4 (c), the thermocouple is connected to the receiving instrument via a compensating lead wire having a thermoelectromotive force characteristic equivalent to that of the thermocouple, which is connected to the cold junction side. In this method, as in the method of Fig. 4 (a), it is necessary to compensate for the cold junction temperature, a temperature sensor is attached to the cold junction location, and the compensation voltage based on the temperature signal is converted into the thermocouple electromotive force. Is added. In fact, in most cases, Figure 4 (c)
The compensating lead wire method is applied.

[0003]

In the conventional compensating lead wire system, it is necessary to attach a temperature sensor to the cold junction in order to compensate the cold junction. Therefore, in a receiving instrument for measuring multi-point temperature with high accuracy. , A temperature sensor related to the cold junction point corresponding to each thermocouple is required. Here, the cold junction portion is located on the back surface of the receiving instrument, and its temperature is usually slightly different depending on the position depending on the ambient temperature condition or the temperature condition inside the receiving instrument. Therefore,
In the conventional example, particularly in the case of multipoint temperature measurement using a thermocouple, the cost increases due to the increase in the number of temperature sensors. The calculation of the compensation voltage based on each cold junction temperature is performed by software on the receiving instrument side.
Does not affect cost increase.

An object of the present invention is to solve the above problems of the prior art, and to provide a thermocouple-connected receiver instrument in which the number of actually installed cold junction compensation temperature sensors is reduced to reduce the cost. Especially.

[0005]

According to a first aspect of the present invention, there is provided a thermocouple-coupled receiving instrument in which a plurality of thermocouples are respectively connected via compensating conductors and cold junction compensation is performed for each thermocouple. A thermosensor for detecting the temperature of the cold junction, and an output unit for outputting the cold junction compensation voltage based on the detection signal of the temperature sensor, and a plurality of predetermined ones among all thermocouples. Cold junction compensating means corresponding only to the thermocouple; cold junction compensating voltage for compensating the output of each thermocouple except the predetermined thermocouple relating to the cold junction temperature, and an output part of the cold junction compensating means Computing means for calculating based on the cold junction compensation voltage output from.

A thermocouple-connected receiver instrument according to claim 2 is
The receiving instrument according to claim 1, wherein the calculation means is based on a positional relationship between the cold junction points and a cold junction compensation voltage output from the output part of the cold junction compensation means, based on an interpolation method or an extrapolation method. It is a method of calculating by applying. The thermocouple-coupled receiving instrument according to claim 3 is the receiving instrument according to claim 1 or 2, wherein the number of cold junction compensating means is two if the temperature tendency at each cold junction is linear.

[0007]

According to the thermocouple-connected receiving instrument according to any one of claims 1 to 3, the calculation means is provided for compensating the output of each thermocouple except the predetermined thermocouple, which is related to the cold junction temperature. Each cold junction compensation voltage is calculated based on the cold junction compensation voltage output from the output unit of the cold junction compensation means.

Particularly, in the thermocouple-connected receiving instrument according to the second aspect, the cold junction compensation voltage relating to each thermocouple except the predetermined thermocouple is calculated by the calculating means and the positional relationship between the cold junction points and the cold junction compensation. It is calculated by applying an interpolation method or an extrapolation method based on the cold junction compensation voltage output from the means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a thermocouple-connected receiver instrument according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the embodiment. In the figure, 1 to 5 are thermocouples and 11 to 15 are adders, which add the cold junction compensation voltage based on the temperature of the cold junction to the thermoelectromotive force of each thermocouple. Reference numerals 22 and 24 denote cold-junction compensating means corresponding to the thermocouples 2 and 4, which are composed of temperature sensors 32 and 34 and output sections 42 and 44 which output cold-junction compensation voltage based on the temperature signals. . 10 is a calculation means, each thermocouple 1,3, excluding each thermocouple 2,4
For the output of 5, the cold junction compensation voltage for compensation relating to the cold junction temperature is calculated based on the cold junction compensation voltage output from each cold junction compensating means 22 and 24. In other words, in this embodiment, the cold junction compensating means and thus the temperature sensor for the cold junction correspond to only 2 out of 5 total thermocouples, and the remaining
The cold junction compensation voltages corresponding to the three are output by the calculating means 10.

The calculation method of the calculation means 10 will be described with reference to FIG. The figure is a characteristic diagram of the compensation voltage / cold junction location showing the calculation of the cold junction compensation voltage of the embodiment. In the figure, the vertical axis represents the compensation voltage Vc related to the cold junction, and the horizontal axis represents the cold junction location (or thermocouple) number i. Each cold junction point 2,
Let Vc2 and Vc4 be the compensation voltages based on the measured temperature by the temperature sensors 32 and 34 (see Fig. 1) in 4, and apply the interpolation method and the extrapolation method by the straight line connecting these two points to each other. The compensation voltages related to the cold junction points 1, 3, and 5 are estimated to be Vc1, Vc3, and Vc5 without measuring the respective temperatures. The respective compensation voltages are input to the respective adders 11, 13, 15 and added to the electromotive force of the corresponding thermocouples 1, 3, 5, respectively. This estimation is based on the fact that the position of each cold junction is juxtaposed in the vertical direction on the back surface of the receiving instrument and each temperature drops linearly with the number.

The operation of the embodiment will be described mainly with reference to the flowchart of FIG. 2 and supplementarily to the configuration diagram of FIG. In Figure 2, in step S1, each number
Cold junction temperatures Θ2 and Θ4 of 2 and 4 are input, and step S2
Then, the corresponding voltages Vc2 and Vc4 for cold junction compensation are input. In step S3, a calculation for estimating the compensation voltages Vc1, Vc3, Vc5 is performed without measuring the temperature.
That is, Vc1 = Vc2 + (Vc2-Vc4) / 2 = (3Vc2-Vc4) / 2 Vc3 = (Vc2 + Vc4) / 2 Vc5 = Vc4- (Vc2-Vc4) / 2 = (3Vc4-Vc2) / 2 Next step S4 Then, the number i related to the thermocouple or cold junction part is initialized (= 1), and in step S5, the thermocouple i
The thermal electromotive force Ti of is input. In step S6, the corrected thermoelectromotive force (Ti + Vci) is obtained, and the subsequent steps S7,
Go to S8 and repeat steps S5, S5 for all five thermocouples.
S6 is repeated, and then the above is repeated.

[0012]

According to the thermocouple-connected receiving instrument of any one of claims 1 to 3, the output of each thermocouple except the predetermined thermocouple is compensated for the cold junction temperature by the calculating means. Each of the cold-junction compensating voltages for the above is calculated based on the cold-junction compensating voltage output from the output part of the cold-junction compensating means. Therefore, the temperature sensor for cold junction compensation is
Since it is not used for each thermocouple except the predetermined thermocouple, the number of temperature sensors actually installed can be reduced by that much, and the cost can be reduced. In addition, the output of the cold junction compensation means,
Since all the arithmetic means are configured as software, the cost effect is extremely small.

Particularly, in the thermocouple-connected receiving instrument according to the second aspect, the cold junction compensation voltage relating to each thermocouple except the predetermined thermocouple is calculated by the calculating means and the positional relationship between the cold junction points and the cold junction compensation. The accuracy of the cold junction compensation is high because it is calculated by applying the interpolation method or the extrapolation method based on the cold junction compensation voltage output from the means. In particular, in the thermocouple-connected receiving instrument according to claim 3, if the temperature tendency of each cold junction is linear, only two cold junction compensating means, and thus the temperature sensor actually installed, are required, which leads to cost reduction. Be supported.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment according to the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment.

FIG. 3 is a compensation voltage showing a cold junction compensation voltage calculation of the embodiment.
Characteristic diagram of cold junction

FIG. 4 is a schematic diagram of a direct method, (b) is a schematic diagram of a copper conductor method, and (c) is a schematic diagram of a compensating conductor method regarding thermocouple connection methods.

[Explanation of symbols]

 1-5 Thermocouple 10 Calculation means 11-15 Adder 22 Cold junction compensation means 32 Temperature sensor 42 Output part 24 Cold junction compensation means 34 Temperature sensor 44 Output part

Claims (3)

[Claims] 1. A receiving instrument in which a plurality of thermocouples are respectively connected via compensating conductors and cold junction compensation is performed for each thermocouple, and a temperature sensor for detecting the temperature of a cold junction, and A cold junction compensating means having an output section for outputting a cold junction compensation voltage based on a detection signal of the temperature sensor and corresponding to only a plurality of predetermined thermocouples among all the thermocouples; Calculating means for calculating each cold junction compensation voltage for compensating the cold junction temperature for the output of each excluding thermocouple, based on the cold junction compensation voltage output from the output part of the cold junction compensating means; A thermocouple-connected receiver instrument characterized by comprising: 2. The receiving instrument according to claim 1, wherein the calculating means interpolates based on the positional relationship between the cold junction points and the cold junction compensation voltage output from the output part of the cold junction compensating means. A thermocouple-connected receiver instrument characterized in that it is a method of calculation by application of the method or extrapolation method. 3. The receiving instrument according to claim 1, wherein the number of cold junction compensating means is two if the temperature tendency of each cold junction location is linear. Receiving instrument.