JPH08152365A - Method for calibrating resistance temperature sensor - Google Patents

Abstract

PURPOSE: To make it possible to graduate the scale in the industrial resistance temperature sensor by a fixed point method by calibrating the specified temperature range scale of the industrial resistance temperature sensor specified in JIS at the three fixed points of the triple points of water, Ga points and In points, and regressing and fixing the intermediate temperature scale by the specified expression. CONSTITUTION: The temperature range scale of the industrial resistance temperature in 0-200 deg.C specified in JIS is calibrated at the three fixed points of the triple points of water, Ga points and In points. The intermediate temperature scale is obtained by substituting the resistance values obtained at the three fixed points into the quadratic expression of the expression: Rt=R0.01+at+bt<2> , obtaining the coefficients of (a) and (b) and substituting the resistance values corresponding to the temperature values to be obtained into the quadratic expression, respectively. In the expression, R0.01 indicate the resistance values at the triple points of the water, and Rt indicates the resistance value at t deg.C. Since the temperature range scale of the resistance temperature sensor is directly calibrated at the three fixed points and the intermediate temperature is redressed and fixed by the quadratic expression in this way, extra parameters do not enter, and the highly accurate calibration can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calibration method capable of highly accurate temperature standard setting for a resistance temperature detector defined in JIS C1604 and a sheath resistance temperature detector defined in JIS C1606.

[0002]

2. Description of the Related Art A temperature scale is defined by a reference temperature, that is, a fixed point, and a thermometer that interpolates a temperature between fixed points, that is, a standard thermometer. A standard platinum resistance thermometer is used as the standard thermometer for the resistance thermometer, and the In point (429.74
Up to 85K, triple point of water (273.16K), Ga point (302.
There are 3 fixed points (9146K), and the resistance value at these temperature fixed points is measured. The interpolation formula is given by the resistance ratio at the triple point of water. Using this interpolation formula (the interpolation formula of ITS-90) for obtaining the coefficient from the resistance ratio W (t) at each fixed point, the temperature values other than the fixed points are obtained. As conditions for standard platinum resistance thermometer,
W (29.7646 ℃) ≧ 1.11807 is specified. Next J
Platinum resistance thermometer specified in ISC1604 and JISC1606
There is a comparative calibration method as a method for pricing the sheath platinum resistance thermometer as specified in paragraph 1.The platinum resistance thermometer calibrated by the fixed point method is used as a standard thermometer to accurately measure the oil bath temperature. At that time, the temperature value is obtained by comparing the obtained resistance value of the thermometer to be calibrated, that is, the platinum resistance thermometer with the standard calibration value. In the comparative calibration, it is general to measure at a required temperature point to obtain a calibration value. By the way, the specifications of ITS-90 as an interpolating thermometer [W (29.7646 ° C) ≧ 1.11807]
A long-stem type standard platinum resistance thermometer that satisfies the above conditions is expensive, sensitive to vibration, requires careful handling, and requires some knowledge and experience for heat treatment. It is difficult to use except for the purpose. Also, since the comparative calibration method is performed in an oil bath, the temperature of the oil bath varies, and there is a time lag in reading when calibrating from the standard thermometer to the calibrated thermometer. There is a difference in response due to the difference in the structure and material of the thermometer to be calibrated, so the calibration accuracy is worse than that of the fixed point method. further,
Until now, there has been no particular formula for interpolating intermediate points other than calibration points.

[0003]

Therefore, according to the present invention, the long-stem type platinum resistance thermometer for standard use is not used but the scale is directly applied to the industrial resistance thermometer stipulated in JIS C 1604 and 1606 by the fixed point method. The present invention intends to provide a method of calibrating a resistance temperature detector that can be used.

[0004]

A method of calibrating a resistance temperature detector according to the present invention for solving the above-mentioned problems is disclosed in JISC 1604, 16
The temperature scale range of industrial resistance temperature detectors specified in 06 from 0 ° C to 200 ° C is set at triple point of water (H ₂ O, T.P.) 0.01 ° C, G
a point (MP) 29.7646 ° C., In point (FP) 156.
Calibrate at 3 fixed points of 5985 ℃, then Rt = R0.01 + at + b
Substituting the resistance value obtained at the three fixed points into the quadratic equation of t ² , a, b
Is obtained by substituting the resistance values for the respective temperature values obtained in the above quadratic equation. In the quadratic equation Rt = R0.01 + at + bt ² , R0.01 represents the resistance value at the triple point of water, and Rt represents the resistance value at t ° C.

[0005]

As described above, according to the method of calibrating the resistance temperature detector of the present invention, the temperature range scale of 0 ° C to 200 ° C of the industrial resistance temperature detector specified in JIS C1604 and 1606 which is the thermometer to be calibrated is directly set. Since the calibration is performed at a fixed point and the intermediate temperature is regressed by the quadratic equation and the value is set, extra parameters do not enter and highly accurate calibration is possible.

[0006]

EXAMPLE An example of the method of calibrating the resistance temperature detector of the present invention will be described. Table 1 below shows the results of the fixed point calibration of the commercially available sheath platinum resistance thermometer sensor specified in JIS C1606 with an outer diameter of φ3.2 mm.

[0007]

[Table 1]

Using the measurement results, the intermediate temperature of 0 ° C. to 200 ° C. is defined by JISC1606 as a quadratic equation and ITS-90.
Comparative calibration performed in an oil bath using the standardized long-stem type platinum resistance thermometer for fixed-point calibration that satisfies the conditions of the ITS-90 interpolating thermometer The test results are shown in Table 2.

[0009]

[Table 2]

The quadratic regression value in Table 2 is obtained by regressing the calibration results of the three fixed points in Table 1 by a quadratic equation to calculate the resistance value with respect to the comparative temperature. The ITS-90 regression value is shown in Table 1. H ₂ O,
T. P. And InF. P. The resistance value with respect to the comparative temperature is calculated by the regression formula of ITS-90 using the value of. The regression formula of ITS-90 is W (29.7646 ℃) ≧ 1.118
When satisfying 07, H ₂ O, T. P. And In point (FP)
And expressions ITS-90 obtained from the two _points, H 2 _O, T. P.
There is an ITS-90 formula that is obtained from two points, namely, the Ga point and the Ga point (MP). If you draw a graph as shown in Fig. 1, the regression line of the latter formula is accurate to within 0.1 mk on the former regression line. Matches with. The image of the quadratic regression line in the graph of FIG. 1 is shown by a chain double-dashed line. When the quadratic regression value and the ITS-90 regression value are graphed using the comparative measurement value of Table 2 as a reference value, it becomes as shown in FIG. When the ITS-90 regression value is graphed, it becomes as shown in FIG. As can be seen from FIGS. 2 and 3, the quadratic regression value is close to the comparative measurement value. still,
At 89.7208 ° C in Table 2, the difference between the comparative measurement value and the quadratic regression value is 4.4 mk, which is larger than the difference at other temperatures, which indicates that the comparative measurement tends to vary. Table 3 below
The calibrated thermometer regressed by the ITS-90 equation is 19 ℃
It is expressed in steps of 1 ° C up to 190 ° C, and Table 4 shows the calibration of the thermometer to be calibrated at three fixed points by regression with a quadratic equation, and it is expressed in steps of 1 ° C from 0 ° C to 200 ° C. is there.

[0011]

[Table 3]

[0012]

[Table 4]

[0013]

As can be seen from the above description, according to the method for calibrating a resistance temperature detector of the present invention, the temperature range from 0 ° C to 200 ° C
By regressing the calibration results of the three fixed points by the quadratic equation to the industrial resistance thermometer specified in ISC1604, 1606, the temperature standard can be set with high accuracy even for the intermediate temperature.

[Brief description of drawings]

FIG. 1 is a graph showing a regression line of ITS-90 and a quadratic regression line.

FIG. 2 is a graph of a quadratic regression value and an ITS-90 regression value using the comparative measurement value in Table 2 as a reference value.

FIG. 3 is a graph showing the comparative measurement value and the ITS-90 regression value using the quadratic regression value in Table 2 as a reference value.

Claims (1)

[Claims] 1. A temperature range graduation of 0 ° C. to 200 ° C. of an industrial resistance thermometer stipulated in JIS C 1604 and 1606 has a triple point of water (H ₂ O, T.P.) and a Ga point (M.P. ), The In point (FP) is calibrated at three fixed points, and the intermediate temperature scale is set to R
A method of calibrating a resistance temperature detector, characterized by regressing with a quadratic equation of t = R0.01 + at + bt ^{2 and} setting a value. (However, Rt
Is the resistance value at t ° C, R0.01 is the resistance value at the triple point of water)