JP2654779B2 - Thermoelectric generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermo-electromotive force generator that generates thermo-electromotive force used for calibrating various thermocouples and the like.

[Conventional example] Conventionally, this type of thermo-electromotive force generator obtains thermo-electromotive force data corresponding to a set value set by a setting device based on, for example, data read from a data table provided in a memory, This thermoelectromotive force data is converted into an analog voltage by a D / A converter. In this case, since the thermoelectromotive force of the thermocouple is on the order of μV, and if the voltage is directly output as a voltage, the effect of offset and noise is large, the analog voltage is further converted to a constant current through a constant current circuit. The constant current is converted into a voltage by a current-voltage converter (for example, a resistor) to obtain a desired thermoelectromotive force.

By the way, as a method of obtaining the thermoelectromotive force data,
The thermocouple generates a non-linear thermoelectromotive force with respect to the detected temperature, so one approximate expression corresponding to this non-linearity is obtained,
A method of obtaining the approximate expression using a program, or
As shown in Japanese Patent Application No. 55-43477, there is a method in which a voltage table corresponding to a temperature of a set value is provided in a memory at every predetermined temperature interval, and data is read from this voltage table and calculated by a simple formula.

[Problems to be solved by the invention] However, in the case of the method using the above approximate expression,
Although the memory capacity is small, there is a problem that the calculation processing time until calculating the thermoelectromotive force data becomes long. In the case of Japanese Patent Application Laid-Open No. 55-43477, data for conversion is stored in a memory at every predetermined temperature (for example, 25 ° C.) step. However, there is a problem that the capacity of a memory for storing the data becomes large. In addition, there is a problem in that if the set temperature range is widened, data for conversion for each step increases, and the memory capacity similarly increases.

The present invention has been made in view of the above problems, and has as its object to reduce the memory capacity and obtain thermoelectromotive force data with less error in a short time. An object of the present invention is to provide a thermo-electromotive force generator configured to generate power.

[Constitution of the Invention] In order to achieve the above object, the present invention reads various data corresponding to a set temperature value set by a setter from a memory, and performs predetermined arithmetic processing on the data by an arithmetic control means to perform various operations. In the thermo-electromotive force generator for generating thermo-electromotive force of a thermocouple, the memory stores a plurality of temperature point data for determining data to be used for calculation with respect to the set temperature value. A temperature point data storage area stored at intervals of a temperature width corresponding to a change rate of a power curve, and an offset value storing reference thermoelectromotive force (offset value) data of a thermocouple for each of the temperature point data. A data storage area and a rate-of-change data storage area in which the rate-of-change data of the reference thermoelectromotive force is stored for each of the temperature point data are provided, and the arithmetic control means is set by the setting unit. The set temperature value thus set is compared with each of the temperature point data to determine a temperature range including the set temperature value, and the offset value data storage area and the change rate data storage area are used to determine the temperature range within the temperature range. It is characterized in that the offset value data and the rate-of-change data are read out, respectively, and the thermoelectromotive force data corresponding to the set temperature value is calculated based on the two data.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 denotes arithmetic control means (CPU). The arithmetic control means 1 has data of a set temperature value set by a setter 2 and a reference point of a thermocouple obtained by an RJ (Reference Junctioh) detector 3. Correction data has been entered.
The arithmetic control means 1 has a memory 4 for storing data for calculating thermoelectromotive force data based on the setting device 2.
Is connected. As shown in FIG. 2, the memory 4 has a temperature point data storage area 4a for storing temperature point data for dividing a set temperature range into a plurality (n), and a reference heat of various thermocouples corresponding to the temperature point data. An offset value data storage area 4b for storing electromotive force (offset value) data,
A change rate data storage area 4c for storing change rate data of the thermoelectromotive force during the division is provided. The data stored in these areas may not be at intervals of a constant temperature as shown in the table of FIG. 4, and for example, may be small where the change of the differential value of the standard thermoelectromotive force curve with respect to the temperature is small. it can.

On the other hand, the arithmetic control means 1 outputs the thermoelectromotive force data obtained by the arithmetic processing to the D / A converter 5. The D / A converter 5 converts the thermoelectromotive force data into an analog voltage and converts the data into a constant current circuit 6.
Output to The constant current circuit 6 outputs a constant current proportional to the analog voltage to the current-voltage converter 7. The current-voltage converter 7 outputs the thermoelectromotive force of the thermocouple corresponding to the set temperature value set by the setter 2.

Next, the operation of the thermoelectromotive force generator will be described with reference to the flowchart of FIG.

First, the arithmetic and control unit 1 performs an initial setting (step ST
1). At this time, it is assumed that the reference point correction has not been set. Next, when the setter 2 is operated, the set temperature value _Tx data thus set is inputted (step ST).
2) Temporarily store the data in, for example, a register or a predetermined area of the memory 4. Then, the set temperature data T _x stored in a predetermined area of the temperature point data T _n and the register or memory 4 sequentially read from the temperature point data area 4a of the memory 4 compares each case, to the set temperature value data One corresponding temperature range ( _Tn-1 ≦ _Tx < _Tn or _Tn−1 < _Tx ≦ _Tn ) is determined (step ST3). Here, in the K thermocouple chart shown in FIG. 4, for example, when the set temperature value T _x is assumed to be 300 ° C., the temperature range of the set temperature T _x is T _n-1 = 215
° C and Tn = 411 ° C. Then, T _x = T _x −T
A calculation process of _n-1 (= 85 ° C.) is executed (step ST5), and based on the calculation result, a change rate data storage area of the memory 4
From step 4c, change rate data α (= 41.44) between T _n-1 (= 215 ° C.) and Tn (= 411 ° C.) is read out (step ST5), and the memory 4
From the offset value data storage area 4b of the temperature point data T _n-1
The offset value data V _Tn-1 (= 215 ° C.) is read out (step ST6). Based on these data, V _Tx = α · T _x + T
Execute the calculation processing of _Tn-1 (= 12259.4μV) (step S
T7), and calculates the thermal electromotive force data V _Tx. That is, the thermoelectromotive force data corresponding to between temperature point data T _n-1, T _n is obtained by a value corresponding to the straight line l shown in Figure 5. Here, since the reference point correction is not set (step ST8), the thermoelectromotive force data V _Tx is output to the D / A converter 5 (step ST8).
9). At this time, the thermoelectromotive force data V _Tx is stored in the D / A converter 5.
For example, a rounded value (V _Tx = 122)
59) is output.

The thermoelectromotive force data V _Tx thus obtained is converted into an analog voltage by the D / A converter 5, and the analog voltage is converted by the constant current circuit 6 into a constant current proportional to the thermoelectromotive force data V _Tx. Is converted to Further, a constant current proportional to the thermoelectromotive force data V _Tx is converted into a thermoelectromotive force by the current-voltage converter 7. Here, the current-voltage converter 7 is R ₁ (100Ω) −R
_{In the case of a 2} (1Ω) resistor circuit, the output current of 12.259 mA from the constant current circuit 6 is 1.2259 across both ends of the resistor R _1.
V, 12.259mV is output across the resistor R _2. Note that 300
The standard thermoelectromotive force of the JIS K thermocouple at ° C. is 12.207 mV. In this case, the approximation error is an extremely large value in this embodiment, but falls within the range of an allowable error condition described later as shown in FIG. 6 (c). The current - in the voltage converter 7, the use of voltage of the resistor R ₁ as a negative feedback constant current operation, the voltage is large, it takes a sufficient S / N ratio, stability.

In performing the arithmetic processing of the thermoelectromotive force data V _Tx = α · T _x + V _Tn−1 , instead of steps ST4 to ST7,
The change rate data α between T _n-1 and Tn and the offset value data V _Tn-1 at the time of T _n-1 are stored in the change rate data storage area 4 of the memory 4 respectively.
c and the offset value data storage area 4b (steps ST10 and ST11), and based on this data, the arithmetic processing of the thermoelectromotive force data V _Tx = α · (T _x −T _n ) + V _Tn-1 is executed (step S 10). ST12).

On the other hand, if the thermocouple reference point correction is set,
In step ST8, a reference point correction routine is entered. In this reference point correction routine, the arithmetic processing means 1 first converts the thermoelectromotive force data V _Tx obtained in the arithmetic processing of step ST7 into V _Tx '.
Is temporarily stored in a register or a predetermined area of the memory 4 (step ST13). Next, the reference point corrected temperature value data T _RJ output from the RJ detector 3 is input (step ST1).
4), and T _x = T _RJ (step ST15). Then, its T _x
Based on step ST16, step ST17, step ST18,
In step ST19 and step ST20, the above step ST3
→ Perform the same processing as ST4 → ST5 → ST6 → ST7. In this case, the temperature point data T _n−1 , T _n , the change rate data α, and the offset value data V _Tn−1 , V _Tn are a reference point correction temperature point data area provided in a predetermined area of the memory 4, The data stored in the data change rate data area and the reference point correction offset value data area (not shown) are used. Then, the correction heat electromotive force data V _Tx for temperature correction is calculated at step ST20. Subsequently, a process of calculating a -V _Tx 'V _Tx = V _Tx by a' and the corrected thermal electromotive force data V _Tx emf data V _Tx which has already been stored calculated to a predetermined area of the register or memory 4 (Step ST21). By this calculation, the thermoelectromotive force data subjected to the reference point correction is obtained. Then, the thermoelectromotive force data V _Tx is output to the D / A converter 5 (step ST9). Hereinafter, a predetermined thermoelectromotive force is generated in the D / A converter 5, the constant current circuit 6, and the current-voltage converter 7 in the same manner as described above based on the calculated thermoelectromotive force data. in this case,
The thermoelectromotive force becomes a more accurate value because the reference point is corrected.

Steps ST4 to ST7 are replaced with step ST7.
In the same way as changing from step 10 to step ST12, the calculation of the reference point corrected thermoelectromotive force data is performed from step STS17 to step ST2.
It may be obtained by performing the processing from step ST22 to step ST24 instead of 0.

As described above, the present invention linearly approximates the standard thermoelectromotive force of a thermocouple at predetermined temperature intervals. Therefore, in this linear approximation, if the temperature interval is wide where the change of the differential value of the standard thermoelectromotive curve is small, and if the temperature interval is narrow where the change of the differential value of the standard thermoelectromotive curve is large, the standard thermoelectromotive force line Can be very close to

Next, the linear approximation error (difference between the standard thermoelectromotive force of the K thermocouple and the calculated value) calculated by the thermoelectromotive force generator based on the data in the chart of FIG. 4 is shown in FIGS. It is shown in the graph of (c). This was obtained under the conditions of an allowable error of ± 0.1% ± 1 ° C., where S ₁ is a limit curve of + 0.1% + 1 ° C., and S ₂ is a limit curve of −0.1% −1 ° C. Error curve L
Is clearly within ± 0.1% ± 1 ° C. from the graph.

[Effects of the Invention] As described above, according to the thermoelectromotive force generator of the present invention, the temperature point data for dividing the set temperature range, the reference thermoelectromotive force (offset) of various thermocouples corresponding to the temperature point data, Value) data, and the rate of change of the reference thermoelectromotive force data is used to calculate the thermoelectromotive force data corresponding to the set temperature value by a linear equation. The power data can be calculated, and the thermoelectromotive force generation error can be reduced.

Further, according to the thermoelectromotive force generation device of the present invention, the temperature point data and the like can be reduced in a portion where the differential value of the standard thermoelectric power curve of the thermocouple is small, and the thermoelectromotive force generation can be performed without increasing the memory. The error can be kept small.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a thermoelectromotive force generator showing one embodiment of the present invention, FIG. 2 is a memory diagram showing a memory configuration of the thermoelectromotive force generator, and FIG. FIG. 4 is a chart showing an example of data stored in the memory, FIG. 5 is a characteristic diagram of the thermoelectromotive force by the thermoelectromotive force generator, and FIGS. (C) is a graph showing an error of the thermoelectromotive force generator. In the figure, 1 is an arithmetic control means (CPU), 2 is a setting device, 3 is R
・ J detector, 4 is a memory, 4a is a temperature point data storage area,
4b is an offset value data storage area, 4c is a change rate data storage area, and 5 is a D / A converter.

Claims (1)

(57) [Claims] 1. A thermoelectric device for reading data corresponding to a set temperature value set by a setter from a memory, performing predetermined arithmetic processing on the data by arithmetic control means, and generating thermoelectromotive forces of various thermocouples. In the power generation device, the memory stores a plurality of temperature point data for determining data to be used for the calculation with respect to the set temperature value, in a temperature range corresponding to a rate of change of a standard thermoelectromotive force curve of the thermocouple. A temperature point data storage area stored at intervals, an offset value data storage area storing reference thermoelectromotive force (offset value) data of a thermocouple for each of the temperature point data, A rate-of-change data storage area in which rate-of-change data of the reference thermoelectromotive force is stored. The arithmetic control means includes a set temperature value set by the setter and each of the temperature point data. To determine a temperature range that includes the set temperature value, and read the offset value data and the change rate data within the temperature range from the offset value data storage area and the change rate data storage area, respectively. A thermoelectromotive force generator that calculates thermoelectromotive force data corresponding to the set temperature value based on the two data.