JPH04318431A - Temperature correcting apparatus for thermocouple - Google Patents

Abstract

PURPOSE:To correctly measure the temperature even when a thermocouple is exchanged. CONSTITUTION:A thermocouple temperature input part 13 outputs a temperature signal based on the electromotive force from a thermocouple 7. A measuring temperature input part 17 outputs a temperature signal based on the electromotive force from a temperature compensating element 9. A correcting value storing part 21 stores a correcting value for correcting the temperature signal based on the electromotive force from the temperature compensating element 9 in accordance with the actually measured value for every using thermocouple 7, and outputs the correcting value to a correcting signal operating part 19 corresponding to the connecting thermocouple 7. The correcting signal operating part 19 corrects the temperature signal from the measuring temperature input part 17 by a correcting signal thereby to operate the correcting signal. A measuring value output part 15 corrects the temperature signal from the thermocouple temperature input part 13 with use of the correcting signal from the correcting signal operating part 19 and obtains a measuring value PV.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a thermocouple temperature correction device, and it is used in temperature measurement instruments such as temperature controllers and temperature indicators, which can connect multiple types of thermocouples to the same input terminal. The present invention relates to a temperature correction device that corrects an input temperature signal.

0002

2. Description of the Related Art For example, as shown in FIG.
Connect the thermocouple 7 to the connection terminals 3e and 3f of the connecting terminals 3e and 3f, or connect the compensating lead wires 5a and 5 with temperature characteristics similar to that of the thermocouple 7.
A temperature compensating element 9 extending from the main body case 1 is arranged in close proximity to the connecting terminals 3e and 3f. The thermocouple 7 is a temperature sensor that generates a voltage according to the temperature difference between the temperature measuring junction 7a and the connection terminals 3e and 3f as reference junctions. There are many types of thermocouples, such as a J thermocouple made of copper and a T thermocouple made of copper/constantan, and these are connected to a positive connection terminal 3e and a negative connection terminal 3f via strands or compensating conductors 5a and 5b.

The temperature compensation element 9 is a temperature measuring resistor, a thermistor, a diode, etc. that measures the ambient temperature of the connection terminals 3e and 3f, and is connected to the correction temperature measurement circuit 1 in the main body case 1.
It extends from 1. Note that the other connection terminals 3a to 3d arranged on the main body case 1 in FIG. 7 are for power connection and operation output, but illustration of the connection state is omitted. Such a temperature controller inputs the temperature of the object to be measured through the thermocouple 7, and connects the connecting terminal 3 to which the compensation conductors 5a and 5b are connected.
Measure the ambient temperature at points e and 3f with the temperature compensation element 9, input it to the correction temperature measurement circuit 11, output a correction signal from the correction temperature measurement circuit 11, and measure the temperature of the object by the following method. Common.

That is, the temperature T of the temperature measuring junction 7a of the thermocouple
The temperature Tx is obtained by adding a correction signal calculated by the correction temperature measurement circuit 11 from the temperature measured by the temperature compensation element 9 to the thermoelectromotive force generated due to the temperature difference between x and the temperature Tcj of the connection terminals 3e and 3f.
are being measured. Here, the temperature measurement thermoelectromotive force ex is expressed as follows. ex=e(Tx, Tcj)+e(Tc, To)
......Formula (1), e(Tx,
Tcj) is the temperature of the temperature measuring junction is Tx, and the temperature of the reference junction is T
e(Tc, To) is the thermoelectromotive force when cj, and e(Tc, To) is when the temperature of the temperature measuring junction is Tc≒Tcj, and the temperature of the reference junction is To=0℃
This is the thermoelectromotive force when .

[0005]The thermoelectromotive force between Tc and To includes errors in the temperature compensating element 9 of the temperature controller and errors in the internal circuit, so it generally differs from one device to the next. Therefore, with respect to the correction signal from the correction temperature measurement circuit 11, the correction value itself is adjusted and stored in advance in accordance with the thermocouple 7 to be used, and this correction signal is added to the thermoelectromotive force between Tx and Tcj,
The value obtained by converting this thermoelectromotive force into temperature is obtained as the measured value PV. Furthermore, a common value is used for all of the plurality of types of thermocouples as the correction value.

[0006]

However, the conventional thermocouple temperature correction method described above has the following problems. That is, when obtaining the temperature measurement thermoelectromotive force ex based on the above-mentioned equation (1), at room temperature, Tcj=(T
The condition was that cj+) = (Tcj-) = Tc (Tcj+ is the temperature of the positive connection terminal 3e, Tcj-
is the temperature of negative connection terminal 3f). However, in reality, Tcj+ and Tcj- are not equal, and (Tcj+)≠(
Tcj-)≠Tc, which is a cause of error. However, these error factors are due to certain thermocouples 7
If only the thermocouple 7 is connected, use the thermocouple 7 as described above.
Since the correction value itself was adjusted in advance before operation in response to this, and the error was removed, the measured value PV was converted and calculated, so there was no problem.

However, in a temperature controller that is planned to connect multiple types of thermocouples, when actually using a thermocouple different from the thermocouple adjusted before operation, T
The temperature difference between cj+ and Tcj- becomes an error factor, and an inaccurate measured value PV is likely to be output. For example, if the temperature controller is adjusted with a K thermocouple before being shipped, and then operated using a T thermocouple after being delivered to the user, the temperature Tcj+ at the positive connection terminal 3e and the temperature Tcj+ at the negative connection terminal 3f may differ. Temperature Tc
The error due to the temperature difference of j- will affect the measured value PV.

In particular, recent temperature controllers allow the user to select one thermocouple from more than 10 types according to the purpose of use, making it possible to obtain error-free measured values P.
A method of calculating and outputting V is desired. Furthermore, as the internal functions of temperature controllers have increased with the trend toward miniaturization, the effects of internal heat generation are likely to appear on the connection terminals 3e and 3f to which the strands or compensation conductors 5a and 5b are connected, and after the power is turned on. Even during stable measurements, there may be a difference of, for example, about 1° C. between the connection terminals 3e and 3f, which are only about 10 mm apart, and this point also needs to be taken into account.

The present invention has been made to solve these conventional drawbacks, and an object of the present invention is to provide a thermocouple temperature correction device that allows accurate temperature measurement even if the type of thermocouple is changed. .

0010

[Means for Solving the Problems] In order to solve such problems, the present invention provides a thermocouple temperature input section for inputting temperature signals from thermocouples connected to the device main body, and a thermocouple temperature input section that inputs temperature signals from thermocouples connected to the device main body. A temperature measurement input section that inputs the temperature signal near the connection point, stores correction values for each of multiple types of thermocouples, and outputs correction values corresponding to the actually connected thermocouples based on the stored values. a correction value storage section that corrects the temperature signal from the temperature measurement input section with the correction value from the correction value storage section to create a correction signal, and a correction signal calculation section that corrects the temperature signal from the thermocouple temperature input section. and a measured value calculation section that calculates the measured value by correcting it using the signal. And, the present invention
The above correction value storage section may be configured to store measurement correction values measured in advance for multiple types of thermocouples and output measurement correction values, or to store measurement correction values for a specific thermocouple and information about other thermocouples. It is preferable to store the correction difference with respect to a specific thermocouple, and to compensate the measurement correction value for each type of thermocouple with the correction difference and output it as a correction value.

[0011]

[Operation] In the present invention equipped with such a means, for example, when a certain thermocouple is connected in a state where measurement correction values measured in advance for a plurality of types of thermocouples are stored in the correction value storage section, the thermocouple is A temperature signal of the thermocouple is output from the temperature input section. The temperature signal near the connection point between the thermocouple and the device body is output from the temperature measurement input section to the correction signal calculation section, and the correction value corresponding to the actually connected thermocouple is sent from the correction value storage section to the correction signal calculation section. Added. In the correction signal calculation section,
The temperature signal from the temperature measurement input section is corrected with the correction value from the correction value storage section, a correction signal is calculated, and is added to the measured value calculation section. The measured value calculation section corrects the temperature signal from the thermocouple temperature input section using a correction signal to calculate the measured value. and,
The correction value storage unit stores the measurement correction value for a specific thermocouple and the correction difference between the specific thermocouple and the other thermocouple, and compensates the measurement correction value for each type of thermocouple using the correction difference. In the configuration configured to output the measured correction values as correction values, there is no need to store the measurement correction values measured in advance for all thermocouples in the correction value storage section.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. The same reference numerals are given to parts common to those in the above description. FIG. 1 is a block diagram showing an embodiment of a temperature correction device according to the present invention. In FIG. 1, a thermocouple temperature input section 13 that amplifies the thermoelectromotive force from the thermocouple 7 and A/D converts it into a digital temperature signal is connected to a measured value calculation section 15. A temperature measurement input section 17 that amplifies the thermoelectromotive force from the temperature compensation element 9 and A/D converts it into a digital temperature signal.
is connected to the correction signal calculation section 19. A correction value storage section 21 is also connected to the correction signal calculation section 19 . This correction value storage section 21 stores thermoelectromotive force from the temperature compensation element 9 for each type of thermocouple 7 connected to the main body case of the temperature controller (see FIG. 7). It is a readable and writable memory that stores in advance a correction value for correcting the temperature signal based on the actual measured value, and outputs it to the correction signal calculation unit 19 according to an instruction from the setting unit 27, which will be described later, in accordance with the thermocouple 7 to be used. It has become.

The correction signal calculation section 19 calculates a correction signal corresponding to the thermocouple 7 from the temperature signal from the temperature measurement input section 17, and corrects it with the correction value from the correction value storage section 21 to calculate the measured value calculation section. 15. The measured value calculation unit 15 adds the correction signal from the correction signal calculation unit 19 to the temperature signal from the thermocouple temperature input unit 13, and calculates and outputs the measurement value PV. Note that since the temperature signals from the thermocouple temperature input section 13 and the correction signal calculation section 19 based on the thermoelectromotive force of the thermocouple 7 and temperature compensation element 9 change non-linearly, the measured value calculation section 15 changes them linearly. Linearization calculation processing is also performed so that changing measured values PV can be obtained.

FIG. 2 is a block diagram showing the above-mentioned temperature correction device together with a temperature controller. The control unit 23 includes a CPU 23a which mainly performs arithmetic control, a ROM 23b storing an operation program for the CPU 23a, and an interface I.
/O23c, and is connected to the thermocouple temperature input section 13, temperature measurement input section 17, storage section 25, setting section 27, display section 29, and output section 31, and controls these. The setting section 27 consists of a keyboard arranged on the main body case, and in addition to inputting the setting value SV, as explained in FIG. At the same time, the type of thermocouple 7 actually connected is selected and set using a code or the like.

The storage unit 25 is a readable and writable memory that operates under the control of the control unit 23, and temporarily stores the set value SV and data of the calculation process of the control unit 23, and also stores information from the setting unit 27. The input correction value for each thermocouple 7 is stored, and functions as the correction value storage section 21 described above. Under the control of the control unit 23, the display unit 29 displays the set value SV input from the setting unit 27, the measurement correction value and correction difference for each type of thermocouple 7, the measurement value PV of the calculation result, the manipulated variable MV, etc. For example, it is a liquid crystal display device.

The output section 31 receives the manipulated variable MV from the control section 23.
A heater (not shown) placed on the measurement target 33 according to the
etc. In addition to the functions described above, the control section 23 takes in the measured temperature signal from the thermocouple temperature input section 13 and the measured temperature signal from the temperature measurement input section 17, and performs correction corresponding to the thermocouple 7 selected by the setting section 27. The value is read from the storage unit 25, the temperature signal from the temperature measurement input unit 17 is corrected with the correction value to calculate a correction signal, and the correction signal is added to the temperature signal from the thermocouple temperature input unit 13 to perform linearization processing. Then, the measured value P
In addition to calculating V, for example, PID calculation is performed according to the deviation between the measured value PV and the set value SV, and the manipulated variable MV is output to the output section 31. That is, the control section 23 functions as the measured value calculation section 15 and the correction signal calculation section 19 in FIG. 1, and also controls the thermocouple temperature input section 13, the temperature measurement input section 17, and the correction value storage section 21.

In such a thermocouple temperature correction device, in FIG. 1, the thermoelectromotive force e(Tx , Tcj) is applied as a digital temperature signal from the thermocouple temperature input section 13 to the measured value calculation section 15, while e(Tc , To) are applied from the temperature measurement input section 17 to the correction signal calculation section 19 as digital temperature signals. In the correction signal calculation unit 19, the correction value ΔTc corresponding to the connected thermocouple 7 is taken in from the correction value storage unit 21, e(Tc) is corrected by ΔTc, a correction signal is calculated, and the measured value calculation unit 15 added to.

Therefore, in the measured value calculation unit 15, Tcj+≠Tcj− of each temperature signal from the thermocouple temperature input unit 13
The error due to this is corrected by the correction signal, and an accurate measured value PV is calculated and output. In the embodiment described above, correction values measured in advance for each type of thermocouple 7 to be connected are stored in correspondence with those thermocouples 7, and the temperature signal based on the thermoelectromotive force from the temperature compensation element 9 is A correction signal is calculated by correcting it with a correction value of the actually connected thermocouple 7, and a temperature signal based on the thermoelectromotive force from the thermocouple 7 is corrected to calculate the measured value PV.

Therefore, even when any type of thermocouple 7 is used, a measured value PV that is always accurately corrected according to the thermocouple 7 actually connected can be obtained. Moreover, since there is no need to take measures to eliminate the temperature difference between the connection terminals 3e and 3f of the main body case 1 regarding the thermocouple 7, the connection terminals 3e and 3f
It also has the advantage of simplifying the nearby configuration. Although the correction value storage unit 21 of the temperature correction device described above is formed to store correction values measured in advance for each connected thermocouple 7, the correction value storage unit 21 in the present invention is not limited to this.

The configuration shown in FIG. 3 focuses on the ratio of electromotive force regarding the positive connection terminal 3e and the negative connection terminal 3f in FIG. This value is stored and used as an additional correction value. That is, a specific measurement value storage section 35 stores a specific correction value measured in advance for a specific thermocouple 7, and a correction difference between the specific thermocouple 7 and the specific thermocouple 7 for other thermocouples 7 among the thermocouples 7 used. The correction value storage section 21 is formed by providing a correction difference storage section 37 and an arithmetic circuit 39 that calculates a correction value by compensating these specific correction values with the correction difference. Note that the other configurations are the same as in FIG. 1, and the specific measurement value storage section 35 and the correction difference storage section 37 are formed by the storage section 25 in FIG. 2, and the control section 23 functions as the arithmetic circuit 39.

The specific correction value stored in the specific measurement value storage section 35 is the same correction value as in the above-mentioned embodiment, and is, for example, K.
The thermocouple is set from the setting section 27 in FIG. The correction difference stored in the correction difference storage section 37 is also stored in the setting section 27 in FIG.
Tables of physical constants (reference electromotive force tables for thermocouples) published in scientific chronology and the like are stored as tabular data as shown in FIGS. 4 and 5, for example.

The correction difference data shown in FIG. 4 is based on the ratio of the absolute thermopower of the material on the positive side and the negative side of the thermocouple at the connection terminals 3e and 3f of the main body case 1 for each thermocouple 7 (hereinafter referred to as the electromotive force). In the temperature correction device shown in FIG. 3, the temperature difference between Tcj+ and Tcj- is compensated by the calculation circuit 39 for the ratio difference between the specific thermocouple used for adjustment and the thermocouple actually connected. and outputs the correction signal to the correction signal calculation section 19. In addition, the electromotive force ratio is the thermocouple 7
When the electromotive force of the metal connected to the positive connection terminal 3e is A, the electromotive force of the metal connected to the positive connection terminal 3e is B, and the electromotive force of the metal connected to the negative connection terminal 3f is C, the electromotive force ratio of the positive connection terminal 3e is B/ In A, the electromotive force ratio of the negative connection terminal 3f is expressed as C/A.

For example, when adjusting the thermocouple 1 in FIG.
As in the thermocouple 1 shown in Fig. 6, the negative connection terminal 3f
When using thermocouple 2, the negative connection terminal 3 is adjusted as shown in Figure 6B for thermocouple 2.
It is necessary to correct the point from f to Y2%, and Tcj+ and T
If the temperature difference of cj- is T, then T x (Y2% - Y1%)
correction is required. Note that the temperature difference T between the connection terminals 3e and 3f can be measured by arranging two temperature compensation elements 9, or
There is a method of adjusting with two types of thermocouples and back calculating the error using the electromotive force ratio shown in FIG.

However, since the variation in the temperature difference T between the connection terminals 3e and 3f is generally relatively small for instruments of the same type, it is more practical to store a certain fixed value in advance. In addition, the correction difference data shown in FIG. 5 is obtained by determining the thermocouple 7 to be used for adjustment in advance and storing the correction ratio for that specific thermocouple.
It is similar to In addition, although the above-mentioned embodiment was explained by taking as an example a device that inputs one thermocouple, the present invention can be similarly implemented in a device that inputs a plurality of thermocouples.

[0025]

Effects of the Invention As explained above, the temperature correction device of the present invention stores, for example, measurement correction values for each of a plurality of types of thermocouples, and also measures temperature using measurement correction values corresponding to the actually connected thermocouples. The temperature signal from the input section is corrected to calculate a correction signal, and the temperature signal from the thermocouple temperature input section is corrected with the correction signal to calculate the measured value, so even if the actually connected thermocouple changes. Accurately corrected measurement values can be obtained for each type of thermocouple. Therefore, a temperature measuring instrument equipped with the temperature correction device of the present invention can measure temperature with high accuracy. In addition, in a configuration that outputs a correction value by compensating the measurement correction value for a specific thermocouple with the correction difference between other thermocouples and the specific thermocouple, the error is adjusted (measured) in advance as in the past.
At least one thermocouple is required, which improves operability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a temperature correction device according to the present invention.

FIG. 2 is a block diagram showing a temperature controller equipped with the temperature correction device of the present invention.

FIG. 3 is a block diagram showing another configuration of the temperature correction device according to the present invention.

FIG. 4 is a diagram showing data stored in a corrected temperature difference storage section in FIG. 3;

FIG. 5 is a diagram showing another data stored in the corrected temperature difference storage section in FIG. 3;

FIG. 6 is a diagram illustrating the operation of the temperature correction device in FIG. 3;

FIG. 7 is a diagram showing a state in which a thermocouple and a temperature compensation element are connected to a temperature controller.

[Explanation of symbols]

1 Main body case 3a, 3b, 3c, 3d, 3e, 3f Connection terminal 5a
, 5b Compensation lead wire 7 Thermocouple 7a Temperature measurement junction 9 Temperature compensation element 11 Correction temperature measurement circuit 13 Thermocouple temperature input section 15 Measured value calculation section 17 Temperature measurement input section 19 Correction signal calculation section 21 Correction value storage section 23 Control section 23a CPU 23b ROM 23c I/O 25 Storage section 27 Setting section 29 Display section 31 Output section 33 Measurement object (control object) 35 Specific measurement value storage section 37 Correction difference storage section 39 Arithmetic circuit

Claims (3)

[Claims] 1. A thermocouple temperature input section that inputs a temperature signal from a thermocouple connected to a device main body; and a temperature measurement input section that inputs a temperature signal near a connection point between the thermocouple and the device main body. , a correction value storage unit that stores values to be corrected for each of the plurality of types of thermocouples and outputs correction values corresponding to the actually connected thermocouples based on the stored values; and a temperature measurement input unit. a correction signal calculation unit that calculates a correction signal by correcting the temperature signal of the temperature signal with the correction value from the correction value storage unit;
A temperature correction device for a thermocouple, comprising: a measured value calculation section that corrects the temperature signal from the thermocouple temperature input section with the correction signal to calculate a measured value. 2. The thermocouple temperature correction device according to claim 1, wherein the correction value storage unit stores measurement correction values measured in advance for a plurality of types of the thermocouples and outputs the measurement correction values. . 3. The correction value storage unit stores a measurement correction value for a specific thermocouple and a correction difference between the specific thermocouple and the specific thermocouple, and stores a measurement correction value for each thermocouple. 2. The thermocouple temperature correction device according to claim 1, wherein the correction value is output as the correction value after compensating with a correction difference.