JPH0862047A - Temperature measuring apparatus - Google Patents

Abstract

PURPOSE: To obtain an apparatus for measuring the temperature accurately without requiring a high order approximate function. CONSTITUTION: Output voltages from a thermopile 5 and a thermister 6 are fed through amplifiers A, B, respectively, and a switching circuit 7 to an A/D converter circuit 8 where they are converted into digital values and stored in a memory section 3. The digital value is converted into a temperature data using an approximate function selected depending on the digital value thus measuring the temperature accurately without requiring any high order approximite function.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a temperature measuring device.

[0002]

2. Description of the Related Art Conventionally, the temperature calculation means of a radiation thermometer using a thermopile sensor records the output characteristics of the sensor with a pseudo black body as a target in advance, and the temperature of the pseudo black body is used as a variable to measure the thermopile. An approximate function of the output characteristic is obtained in advance, and when the temperature is measured, the temperature of the measuring object is obtained by back-calculating the approximate function from the output voltage output by infrared rays from the measuring object.

[0003]

However, since it is difficult to theoretically obtain the output characteristics of the thermopile with respect to the blackbody target, an approximation function based on a linear function is generally used. Has the drawback that the order of the approximation function must be increased in order to increase the accuracy.

However, the storage of the offset value is performed, for example, when the product is shipped from the factory. In such a method, the offset value changes due to a change with time after shipment and a temperature change. There was a drawback that we couldn't handle it if it happened.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature measuring device capable of highly accurate temperature conversion processing without increasing the order of the approximation function.

[0006]

In order to solve the above-mentioned problems, the present invention obtains different approximation functions depending on the magnitude relationship between the cold junction temperature and the temperature to be measured, so that function processing with a small order can be performed. The feature is that even if there is, high-precision temperature conversion processing can be performed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a temperature measuring device according to the present invention, which is a circuit configuration of a radiation thermometer using a thermopile. The control unit 1 including a central processing unit (CPU) executes a program according to a microprogram stored in the ROM 2. The ROM 2 also stores a temperature table (not shown) that stores temperature data corresponding to voltages from the thermistor 6 and the thermopile 5, which will be described later, and an approximate function formula. The storage unit 3 is composed of a RAM and has a storage area as shown in FIG. 2 described later.

The key input section 4 is provided with an emissivity setting key (not shown) for setting the emissivity of the object to be measured and an execution key (not shown) for executing temperature measurement. When is operated, the flowchart of FIG. 3 described later is executed, and the temperature of the object to be measured is measured by the thermopile 5 in a non-contact manner. The measured voltage output of the thermistor 6 measures the temperature of the thermopile itself, that is, the temperature of the cold junction of the thermopile 5. The measured output voltages of the thermopile 5 and the thermistor 6 are sent to the switching circuit 7 via amplifiers A and B, respectively. The switching circuit 7 has a function of a multiplexer, and according to a control signal from the control unit 1, the output voltage of the thermistor 6 sent via the amplifier B and the thermopile 5 sent via the amplifier A. The output voltage of is sequentially supplied to the analog-digital (A / D) conversion circuit 8. A / D
The digital data output from the conversion circuit 8 is sent to the control unit 1, and the control unit 1 calculates the temperature data of the non-measurement object from these data and displays the temperature data on the temperature display unit 10.

FIG. 2 shows a detailed storage area of the storage unit 3, in which the display register 30 for storing the temperature data displayed on the temperature display unit 10 and the voltage from the thermistor 6 are A / D converted. Register 31 for storing the value TM
And a value T obtained by A / D converting the voltage from the thermopile 5.
A register 32 for storing P, a register 33 for storing the temperature data TC of the non-measured object by calculation, a register 34 for storing the temperature data TTM detected by the thermistor 6, and a thermopile output temperature data ΔT. The register 34 and the register 36 in which the emissivity ε set by the emissivity setting key of the key input unit 4 is stored
Is provided.

Next, the operation of the circuit configured as described above will be described with reference to the flowchart of FIG.

First, by using the emissivity setting key of the key input unit 4, the emissivity ε of the measured object is stored in the register 36 of the storage unit 3.
After setting, the thermopile is pointed at the object to be measured whose temperature is to be measured, and when the execute key of the key input section 4 is operated, a control signal is output from the control section 1 to the switching circuit 7, and as shown in step S1, the thermistor The output voltage 6 is sent to the A / D conversion circuit 8 through the amplifier B, the A / D converted digital data TM is sent to the control unit 1, and the register 3
1 is stored. In the next step S2, it is detected whether or not the A / D converted digital data TTM is larger than the digital data corresponding to a predetermined temperature, for example, 10 degrees Celsius, and if it is larger, the process proceeds to step S3. ,
The temperature data TTM detected by the thermistor 6 is stored in the register 34 by performing the calculation using the approximate function stored in the ROM 2 in advance when the temperature is 10 degrees Celsius or more.

The approximation function in this case is TTM = aTM ²
A second-order approximation function of + bTM + c (where a, b, and c are constants in the approximation function in the case of 10 degrees Celsius or more) is used. In step S2, the digital data T
If TM is smaller than the digital data corresponding to a predetermined temperature of 10 degrees Celsius, the process proceeds to step S4 to determine whether the digital data TTM is larger than the digital data corresponding to a predetermined temperature, for example, 0 degrees Celsius. If it is larger, the process proceeds to step S5 and RO
The temperature data TTM detected by the thermistor 6 is stored in the register 34 by performing a calculation using the approximation function stored in M2 in the case of 0 to 10 degrees Celsius.

The approximation function in this case is TTM = dTM ²
A quadratic approximation function of + eTM + f (where d, e, and f are constants in the approximation function from 0 to 10 degrees Celsius) is used.

Further, in step S4, when the digital data TTM is smaller than the digital data corresponding to 0 degrees Celsius, the process proceeds to step S6 and the ROM 2 is stored in advance.
The temperature data TTM detected by the thermistor 6 is stored in the register 34 by performing the calculation using the approximation function stored at 0 ° C. or less.

The approximation function in this case is TTM = gTM ²
A secondary approximation function of + hTM + i (where g, h, and i are constants in the approximation function in the case of 0 degrees Celsius or less) is performed.

Next, in step S7, a control signal is output from the control section 1 to the switching circuit 7, and the output voltage of the thermopile 5 is sent to the A / D conversion circuit 8 via the amplifier A.
The / D converted digital data TP is sent to the control unit 1 and further stored in the register 32. Next step S
At 8, it is detected whether or not the A / D converted digital data TP is larger than the digital data corresponding to 0 degrees Celsius.
Calculation is performed using the approximation function stored in No. 2, and the temperature data ΔT detected by the thermopile 5 is stored in the register 35.

In this case, the approximation function for calculating ΔT is ΔT = jTP ² + kTP + 1 (where j, k, and l are 0V voltage when the blackbody temperature and the cold junction temperature are equal). In the thermopile, it is a constant in the approximation function when the temperature is 0 ° C. or higher. In step S2, if the digital data TP is smaller than the digital data corresponding to 0 degrees Celsius, the temperature data detected by the thermopile 5 is calculated by using the approximation function corresponding to 0 degrees Celsius or less. △ T
Are stored in the register 35.

In this case, the approximate function for calculating ΔT is ΔT = mTP ² + nTP + o (where m, n, and o are 0V when the blackbody temperature and the cold junction temperature are equal to each other. In the thermopile, it is a constant in the approximation function when the temperature is 0 degrees Celsius or less.

In this way, when the temperature data ΔT detected by the thermopile 5 is stored in the register 35, in the next step S11, TTM (temperature of the thermopile 5 itself) + ΔT (black body temperature and cold junction). Difference from temperature) / ε
(Emissivity) is calculated to calculate temperature data TC of the object to be measured, and the temperature data TC is stored in the register 33, and at the next step S12, the temperature display unit 10 is operated.
Then, it is a digital or analog display.

As described above, in the above embodiment, the temperature data of the digital data obtained from the thermistor is calculated using approximation functions having different constants depending on whether the value is in a plurality of ranges. Therefore, even if the approximation function is not a higher-order function, highly accurate temperature data can be obtained, and the thermopile temperature data is also
Since the obtained digital data is obtained by using different approximation functions depending on whether or not the digital data is equal to or more than the digital data corresponding to 0 degree, highly accurate temperature data can be obtained with a simple circuit.

In the above embodiment, the thermistor temperature is 0.
Although different approximation functions are used with 10 degrees as the boundary, different approximation functions can be used in a finer range. Further, the present invention can be incorporated into other electronic devices, for example, electronic devices such as wristwatches, electronic notebooks, pagers, and mobile phones.

[0022]

As described above, according to the present invention, it is possible to obtain highly accurate temperature data without increasing the order of the approximation function for obtaining the temperature data.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a temperature measuring device according to the present invention.

FIG. 2 is a detailed diagram of a storage section of the circuit.

FIG. 3 is a flowchart showing the operation of the above circuit.

[Explanation of symbols]

 1 ... Control part 2 ... ROM 3 ... Storage part 5 ... Thermopile 7 ... Switching circuit 10 ... Display part

Claims (3)

[Claims] 1. A thermopile, temperature signal output means for measuring the temperature of the thermopile itself, and a temperature signal output means for outputting a measurement signal corresponding to the temperature, and a temperature signal output means which are different from each other according to the measurement signal from the temperature signal output means. A first temperature measuring means for obtaining temperature data by performing calculation using an approximate function, and a second temperature measuring means for obtaining temperature data based on a voltage from a thermopile by infrared rays from a temperature measurement object,
A temperature measuring device for obtaining the temperature of the temperature measuring object based on temperature data from the first and second temperature measuring means. 2. The temperature measuring device according to claim 1, wherein the thermopile has a black body portion and a cold junction portion, and the temperature signal output means outputs a measurement signal of the temperature of the cold junction portion. . 3. The temperature measuring device according to claim 1, wherein the approximation function is a predetermined quadratic function.