JP2729599B2 - Thermocouple temperature compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocouple temperature compensator, and more particularly to a thermometer or a thermometer which can selectively connect a plurality of types of thermocouples to the same input terminal. The present invention relates to a temperature correction device that corrects an input temperature signal from a thermocouple.

[0002]

2. Description of the Related Art For example, as shown in FIG. 7, a temperature controller has a connection terminal 3a disposed on a main body case 1 of the temperature controller.
To the connection terminals 3e and 3f, the thermocouple 7 is connected to the elementary wire or the compensating conductors 5a and 5c having a temperature characteristic similar to that of the thermocouple 7.
b, and the temperature compensating element 9 extending from the main body case 1 is used in the vicinity of the connection terminals 3e and 3f. The thermocouple 7 is a temperature sensor that generates a voltage corresponding to a temperature difference between the temperature measuring contact 7a and the connection terminals 3e and 3f as reference contacts. For example, a K thermocouple made of chromel / alumel or an iron / constantan There are many types such as a J thermocouple, a T thermocouple made of copper / constantan, and the like, which are connected to a plus connection terminal 3e and a minus connection terminal 3f via element wires or compensation conductors 5a and 5b.

The temperature compensating element 9 is a temperature measuring resistor, a thermistor, a diode, and the like for measuring the ambient temperature of the connection terminals 3e, 3f.
Extends from 1. The other connection terminals 3a to 3d arranged on the main body case 1 in FIG. 7 are for connection to a power source and for operation output, but the illustration of the connection state is omitted.

In such a temperature controller, the temperature of the object to be measured is input through a thermocouple 7 and the ambient temperature of the connection terminals 3e, 3f to which the compensating leads 5a, 5b are connected is measured by the temperature compensating element 9.
In general, the measured temperature is input to the corrected temperature measuring circuit 11, a correction signal is output from the corrected temperature measuring circuit 11, and the temperature of the object to be measured is measured by the following method. That is, the temperature Tx of the temperature measuring contact 7a of the thermocouple and the connection terminal 3e,
The temperature Tx is measured by adding the 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 by the temperature difference from the temperature Tcj of 3f.

Here, the temperature measurement thermoelectromotive force ex is expressed by the following equation. ex = e (Tx, Tcj) + e (Tc, To) Expression (1) where e (Tx, Tcj) is the thermoelectromotive force when the temperature of the temperature measuring contact is Tx and the temperature of the reference contact is Tcj. And e (T
c, To) is the thermoelectromotive force when the temperature of the temperature measuring contact is Tc ≒ Tcj and the temperature of the reference contact is To = 0 ° C.

Since the thermoelectromotive force between Tc and To includes an error of the temperature compensating element 9 of the temperature controller and an error of the internal circuit, it generally differs from one to another. Therefore, with respect to the correction signal from the correction temperature measuring circuit 11, the correction value itself is adjusted and stored in advance corresponding to the thermocouple 7 to be used, and this correction signal is added to the thermoelectromotive force between Tx and Tcj,
A value obtained by converting the thermoelectromotive force into a temperature is calculated as a measured value PV. Moreover, a common value is used as the correction value for all of the plurality of types of thermocouples.

[0007]

However, the aforementioned conventional thermocouple temperature correction method has the following problems. That is, when the temperature measurement thermoelectromotive force ex is obtained based on the above equation (1), Tcj = (T
(cj +) = (Tcj-) = Tc (Tcj + is the temperature of the plus connection terminal 3e, Tcj-
Is the temperature of the negative connection terminal 3f).

However, actually, Tcj + and Tcj- are not equal but (Tcj +) ≠ (Tcj-) ≠ Tc, which is an error factor. However, these error factors are caused when only a certain thermocouple 7 is connected.
As described above, the correction value itself is adjusted before operation in accordance with the thermocouple 7 to be used, the error is removed, and the measured value P
Since V was calculated, there was no problem. But,
In a temperature controller in which a plurality of types of thermocouples are to be connected, when a thermocouple different from the thermocouple adjusted before operation is actually used, a temperature difference between Tcj + and Tcj− becomes an error factor. Inaccurate measured values PV are likely to be output.

For example, when the temperature controller is adjusted with a K thermocouple before shipping and is operated using a T thermocouple after the temperature controller has been delivered to the user, the temperature Tc of the plus connection terminal 3e is increased.
An error due to a temperature difference between j + and the temperature Tcj- of the negative connection terminal 3f affects the measured value PV. In particular, in recent temperature controllers, a type in which a user selects one thermocouple from ten or more types of thermocouples according to the purpose of use is provided, and a method of calculating and outputting a measurement value PV without error is desired. It is rare.

[0010] Further, since the internal functions have been increased with the trend of miniaturization of the temperature controller, the influence of the internal heat is reduced by the connection terminals 3e, 3f to which the element wires or the compensating wires 5a, 5b are connected.
10m even during stable measurement after power-on
For example, there may be a difference of about 1 ° C. between the connection terminals 3e and 3f which are only separated by about m, and this point also needs to be considered. The present invention has been made in order to solve such a conventional disadvantage, and an object of the present invention is to provide a thermocouple temperature correction device capable of accurately measuring temperature even when the type of thermocouple is changed.

[0011]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention provides a thermocouple temperature input section for inputting a temperature signal from one thermocouple connected to an apparatus body, and the thermocouples. A temperature measurement input unit for inputting a temperature signal near a connection point between the thermocouple and the device body, a setting unit for setting at least the type of thermocouple actually used, and a value to be corrected for each of the plurality of types of thermocouples are stored. A correction value storage unit that outputs a correction value corresponding to the type of thermocouple set by the setting unit, and a correction signal that corrects the temperature signal from the temperature measurement input unit with the correction value from the correction value storage unit. A correction signal calculation unit to be created;
A measurement value calculation unit that calculates a measurement value by correcting a temperature signal from the thermocouple temperature input unit with a correction signal.

In the present invention, it is preferable that the correction value storage section stores a measurement correction value measured in advance for a plurality of types of thermocouples and outputs the measurement correction value. In the present invention having such means, for example, when one thermocouple is connected under a state in which measurement correction values measured in advance for a plurality of types of thermocouples are stored in the correction value storage unit. The thermocouple temperature input unit outputs a thermocouple temperature signal.

A temperature signal in the vicinity of a connection point between the thermocouple and the device body is output from the temperature measurement input unit to a correction signal calculation unit,
A correction value corresponding to the type of thermocouple set by the setting unit is added from the correction value storage unit to the correction signal calculation unit. In the correction signal calculation section, the temperature signal from the temperature measurement input section is corrected by the correction value from the correction value storage section, and a correction signal is calculated, and is added to the measurement value calculation section. The measurement value calculation section calculates the measurement value by correcting the temperature signal from the thermocouple temperature input section with the correction signal.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those described above are denoted by the same reference numerals. FIG. 1 is a block diagram showing one embodiment of a temperature correction device according to the present invention. In FIG. 1, a thermocouple temperature input unit 13 that amplifies the thermoelectromotive force from the thermocouple 7 and performs A / D conversion to a digital temperature signal is connected to the measurement value calculation unit 15. A temperature measurement input unit 17 for amplifying the thermoelectromotive force from the temperature compensating element 9 and performing A / D conversion into a digital temperature signal is connected to a correction signal calculation unit 19. A correction value storage unit 21 is also connected to the correction signal calculation unit 19.

The correction value storage section 21 is provided with a thermocouple temperature input section 13, in other words, a main body case of the temperature controller (see FIG. 7).
Is a readable and writable memory that stores, in advance, a correction value for correcting a temperature signal based on the thermoelectromotive force from the temperature compensation element 9 based on an actual measurement value for each type of thermocouple 7 connected to the
In accordance with the thermocouple 7 to be used, an output from the setting unit 27 described later is output to the correction signal calculation unit 19. The correction signal calculation unit 19 calculates a correction signal corresponding to the thermocouple 7 from the temperature signal from the temperature measurement input unit 17, corrects the correction signal with the correction value from the correction value storage unit 21, and outputs the corrected signal to the calculation measurement value calculation unit 15. Is what you do.

The measurement value calculation unit 15 is a thermocouple temperature input unit 1
The measurement value PV is calculated and output by adding the correction signal from the correction signal calculation unit 19 to the temperature signal from the control signal 3. 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 the temperature compensation element 9 change nonlinearly, the measurement value calculation section 15 linearly changes the temperature signals. Linearization arithmetic processing is also performed to obtain a changing measured value PV.

FIG. 2 is a block diagram showing the above-described temperature correction device together with a temperature controller. The control unit 23 includes a CPU 23a serving as an arithmetic control main body, a ROM 23b storing an operation program of the CPU 23a, an interface I
/ O23c, which is connected to and controls the thermocouple temperature input unit 13, the temperature measurement input unit 17, the storage unit 25, the setting unit 27, the display unit 29, and the output unit 31. The setting unit 27 is composed of a keyboard arranged on the main body case. In addition to the input of the set value SV, a plurality of measurement correction values corresponding to the thermocouples 7 usable as described in FIG.
A specific correction value and a correction difference to be described later are input, and the type of the thermocouple 7 actually connected is selected and set by a code or the like.

The storage unit 25 is a readable and writable memory which operates under the control of the control unit 23. The storage unit 25 temporarily stores and stores the set value SV and data in the operation process of the control unit 23. It stores the input correction value for each thermocouple 7 and functions as the above-described correction value storage unit 21. The display unit 29 controls the setting unit 27 under the control of the control unit 23.
For example, a liquid crystal display device displays the set value SV input from the, the measurement correction value and the correction difference for each type of the thermocouple 7, the measurement value PV of the calculation result, the operation amount MV, and the like.

The output unit 31 receives an operation amount MV from the control unit 23.
Heater (not shown) arranged on the measurement target 33 according to
And so on. The control unit 23 fetches a measured temperature signal from the thermocouple temperature input unit 13 and a measured temperature signal from the temperature measurement input unit 17 in addition to the above-described functions, and performs correction corresponding to the thermocouple 7 selected by the setting unit 27. The value is read from the storage unit 25, the temperature signal from the temperature measurement input unit 17 is corrected with a 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 a linearization process. And the measured value P
In addition to calculating V, the PID calculation is performed, for example, according to the deviation between the measured value PV and the set value SV, and the manipulated variable MV is output to the output unit 31.

That is, the control unit 23 functions as the measurement value calculation unit 15 and the correction signal calculation unit 19 in FIG. 1, and controls the thermocouple temperature input unit 13, the temperature measurement input unit 17, and the correction value storage unit 21. ing. In such a thermocouple temperature compensating device, in FIG. 1, e (Tx, Tcj) is the thermoelectromotive force when the temperature of the temperature measuring contact is Tx and the temperature of the reference contact is Tcj in the above equation (1). Is applied from the thermocouple temperature input unit 13 to the measured value calculation unit 15 as a digital temperature signal, while e (Tc, To) is the thermoelectromotive force when the temperature of the temperature measuring contact is Tc and the temperature of the reference contact is To. From the temperature measurement input unit 17 to the correction signal calculation unit 19 as a digital temperature signal.

If the type of the connected thermocouple 7 is set by the setting unit 27, the correction signal calculation unit 19 fetches the correction value ΔTc corresponding to the thermocouple 7 from the correction value storage unit 21. In rare cases, e (Tc) is corrected by ΔTc, a correction signal is calculated, and the correction signal is added to the measurement value calculation unit 15.
Therefore, the measurement value calculation unit 15 uses the connected thermocouple 7
For each temperature signal from the thermocouple temperature input unit 13
An error due to cj + ΔTcj− is corrected by the correction signal, and an accurate measurement value PV is output.

As described above, in the above-described embodiment, the correction value measured in advance for each type of the connected thermocouples 7 is stored in association with the thermocouples 7 and the actually connected thermocouples 7 are set by the setting unit. 27, the temperature signal based on the thermoelectromotive force from the temperature compensating element 9 is corrected by the correction value of the thermocouple 7 actually connected to calculate a correction signal, and the thermoelectric signal from the thermocouple 7 is calculated. The measured value PV is calculated by correcting the temperature signal based on the electric power. Therefore, even when an arbitrary type of thermocouple 7 is used, an accurate corrected measurement value PV is always obtained according to each thermocouple 7 actually connected.

Furthermore, since there is no need to devise a means for eliminating the temperature difference between the connection terminals 3e and 3f of the main body case 1 for the thermocouple 7, there is also an advantage that the configuration of the connection terminals 3e and 3f and the vicinity can be simplified. Although the correction value storage unit 21 of the above-described temperature correction device is formed to store the correction value measured in advance for each thermocouple 7 connected thereto, the correction value storage unit 21 in the present invention is not limited to this.

The structure shown in FIG. 3 focuses on the ratio of the electromotive force between the plus connection terminal 3e and the minus connection terminal 3f in FIG. 7 described above, and determines the degree of influence of the temperature difference between the connection terminals 3e and 3f for each thermocouple. This is stored as an additional correction value. That is, the specific measurement value storage unit 35 that stores the specific correction value measured in advance for the specific thermocouple 7 and the correction difference between the specific thermocouple 7 and the other thermocouples 7 among the thermocouples 7 to be used are stored. The correction value storage unit 21 is formed by providing a correction difference storage unit 37 and an arithmetic circuit 39 that calculates the correction value by compensating the specific correction value with the correction difference.

The other configuration is the same as that of FIG. 1. The specific measured value storage unit 35 and the correction difference storage unit 37 are formed by the storage unit 25 of FIG. 2, and the control unit 23 functions as an arithmetic circuit 39. The specific correction value stored in the specific measurement value storage unit 35 is the same correction value as in the above-described embodiment, and is set by the setting unit 27 for, for example, a K thermocouple. The correction differences stored in the correction difference storage unit 37 are also set from the setting unit 27 and are obtained from a physical constant table (thermocouple reference electromotive force table) published in a science chronological table, for example, as shown in FIGS. 4 and 5. It is stored as simple table data.

The correction difference data shown in FIG. 4 is based on the ratio of the absolute thermopower of the material on the plus side and the minus 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 electromotive force). In the temperature correction device of FIG. 3, the difference between the ratio between the specific thermocouple used for the adjustment and the thermocouple actually connected (the thermocouple set by the setting unit 27) is Tcj + and Tcj. The temperature difference − is compensated by the arithmetic circuit 39, and the correction signal is output to the correction signal arithmetic unit 19. The electromotive force ratio is defined as follows: A is the electromotive force of the thermocouple 7, B is the electromotive force of the metal connected to the positive connection terminal 3e, and C is the electromotive force of the metal connected to the negative connection terminal 3f. The electromotive force ratio of the connection terminal 3e is indicated by B / A, and the electromotive force ratio of the minus connection terminal 3f is indicated by C / A.

For example, when the adjustment is performed using the thermocouple 1 shown in FIG.
Like the thermocouple 1 shown in FIG. 6, the compensation is adjusted to the point of Y1% from the negative connection terminal 3f. Must be corrected to the points of Tcj + and Tcj−
Assuming that the temperature difference is T, a correction of T × (Y2% −Y1%) is required. The temperature difference T between the connection terminals 3e and 3f
There is a method of measuring by arranging two temperature compensating elements 9 or adjusting with two kinds of thermocouples, and calculating back from the error using the electromotive force ratio of FIG.

However, in general, the variation of the temperature difference T between the connection terminals 3e and 3f is relatively small in an instrument of the same type, so that it is more practical to store a fixed value in advance. The correction difference data shown in FIG. 5 is obtained by previously determining the thermocouple 7 to be used for adjustment and storing the correction ratio for the specific thermocouple. The compensation by the correction difference is the same as in FIG. .

[0029]

As described above, the temperature correction device of the present invention stores, for example, a measurement correction value for each of a plurality of types of thermocouples, and measures the measurement correction value corresponding to the thermocouple set by the setting unit. The temperature signal from the temperature input section is corrected to calculate the correction signal, and the temperature signal from the thermocouple temperature input section is corrected by the correction signal to calculate the measured value.Select the type of thermocouple in the setting section With this setting, even if the thermocouple to be actually connected changes, a measured value automatically and accurately corrected for each type of thermocouple can be obtained. Therefore, in a temperature measuring instrument to which one thermocouple is selectively connected, the temperature can be measured with high accuracy if the temperature correction device of the present invention is mounted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one 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 illustrating data stored in a correction difference storage unit in FIG. 3;

FIG. 5 is a diagram showing another storage data in a correction difference storage unit in FIG. 3;

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body case 3a, 3b, 3c, 3d, 3e, 3f Connection terminal 5a, 5b Compensating lead wire 7 Thermocouple 7a Temperature measuring contact 9 Temperature compensating element 11 Correction temperature measuring circuit 13 Thermocouple temperature input section 15 Measurement value calculation section 17 Measurement Temperature input unit 19 Correction signal calculation unit 21 Correction value storage unit 23 Control unit 23a CPU 23b ROM 23c I / O 25 Storage unit 27 Setting unit 29 Display unit 31 Output unit 33 Measurement target (control target) 35 Specific measurement value storage unit 37 Correction difference storage unit 39 Operation circuit

Claims (2)

(57) [Claims] 1. A thermocouple temperature input section for inputting a temperature signal from one thermocouple connected to a device main body, and a temperature measurement for inputting a temperature signal near a connection point between the thermocouple and the device main body. An input unit, a setting unit for setting at least the type of the thermocouple to be actually connected, and storing a value to be corrected for each of the plurality of types of thermocouples, corresponding to the type of the thermocouple set by the setting unit A correction value storage unit that outputs a correction value to be corrected; a correction signal calculation unit that calculates a correction signal by correcting a temperature signal from the temperature measurement input unit with a correction value from the correction value storage unit; and the thermocouple temperature. A measurement value calculation unit configured to calculate a measurement value by correcting a temperature signal from an input unit with the correction signal, and a temperature correction device for a thermocouple. 2. The thermocouple temperature correction device according to claim 1, wherein the correction value storage section stores measurement correction values measured in advance for a plurality of types of the thermocouples and outputs the measurement correction values. .