JPS6319020A - Temperature control device - Google Patents

Abstract

PURPOSE:To heighten universal applicability, by constituting each input circuit of an input sensor separately, and inputting a signal by switching the input circuit by an analog switch. CONSTITUTION:The titled temperature control device controls a control object by a control quantity supplied from a sensor input part 15. Also, the sensor input part 15 is equipped with two sensor input circuits 20 and 24 which detect the temperature of the control object, and an A/D converter 26 which converts the output of the input circuit to a digital signal. In a thermocouple input circuit 20, a resistance R1, a cold junction compensation resistor R2, and resistances R3-R4 are connected to the terminal of a power source, and its output is inputted to a buffer circuit 22, and an operational amplifier 23 through the analog switches 21a and 21b. Also, a platinum wire input circuit 24 is connected in the same way as the above circuit, from a bridge circuit consisting of resistances R5-R7, and a platinum resistance wire 5, through the analog switches 25a and 25b. In this way, the analog switches 21 and 25 are energized selectively by an input change-over switch 12, and a supplied signal is supplied to the control part through the A/D converter 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a temperature control device characterized by the configuration of a sensor input section.

[Summary of the invention]

The temperature control device according to the present invention configures each input circuit separately so that either a thermocouple or a platinum resistance wire can be used as an input sensor, and switches between them using an analog switch to control the control unit. .

(Prior art and its problems) (Prior art) In conventional temperature control devices, thermocouples, platinum wires, etc. are used as temperature sensors.The sensor input circuit l using thermocouples is, for example, a resistor as shown in Fig. 2. R1, cold junction compensation resistance R
2 and resistors R3 and R4 form a bridge circuit, a thermocouple 2 is connected to one end of the bridge circuit, and the thermocouple 2 is amplified by an operational amplifier 3.

Further, the sensor input circuit 4 using a platinum resistance wire is, for example, a third
As shown in the figure, resistors R5, R6, including platinum resistance wire 5,
A bridge circuit is formed by R7, and the voltage change across the bridge circuit is amplified by the operational amplifier 6 and output to an A/D (not shown).
It is applied to the converter as a voltage signal.

(Problems to be Solved by the Invention) In such conventional temperature controllers, the input circuits differ depending on the sensor used, so it is necessary to prepare a model of the temperature controller that has an input circuit corresponding to each input. However, there was a problem in that the number of models increased.

[Purpose of the invention]

A technical problem of the present invention is to enable any sensor to be used as a temperature sensor by sharing such an input circuit in one temperature control device.

[Structure and effects of the invention]

(Structure of the Invention) The present invention is a temperature control device that controls the temperature of a controlled object to a predetermined value, and as shown in FIGS. 1 and 4, a thermocouple is used as a sensor and output corresponding to the thermoelectromotive force. a thermocouple input circuit that uses a platinum resistance wire as a sensor and provides an output corresponding to the resistance value; and a platinum wire input circuit that uses a platinum resistance wire as a sensor and provides an output corresponding to the resistance value; a sensor input section having an analog switch for uniform switching; input switching means for providing a switching signal for switching the thermocouple input circuit and the platinum wire input circuit to the analog switch of the sensor input section; and a selected thermocouple input circuit. Alternatively, the present invention is characterized by having a control section that controls the controlled object to a predetermined value based on sensor input from the platinum wire input circuit.

(Function) According to the present invention having such characteristics, it has a bridge type input circuit using a thermocouple and a platinum resistance wire as sensors, and connects either sensor to convert the output into an analog signal. The signal is selectively amplified via a switch and input to the control section.

(Effects) Therefore, according to the present invention, either a thermocouple or a platinum resistance wire can be selectively used as a sensor by simply switching a switch. Therefore, there is no need to prepare a different temperature control device for each sensor, which reduces the number of models and facilitates their management.

[Explanation of Examples]

FIG. 4 is a block diagram showing the configuration of a temperature control device according to an embodiment of the present invention. In this figure, temperature control device 10
is a setting device 11 for setting the control amount of the controlled object. Input selector switch 1 that switches the input sensor between thermocouple and platinum resistance wire
2. A display unit 13 that displays set values and the temperature of the controlled object. A sensor input section 15 that detects the temperature of the controlled object 14 and converts it into a digital signal. The controller 17 stores the set value set by the setting device 11 in a memo I 716 and controls the controlled object 14 according to the control amount given from the sensor input section 15, and a heater etc. is connected to the controlled object 14. An output section 18 is provided to directly control the. The control unit 17 includes a central processing unit (hereinafter referred to as CPU), and the memory 16 includes a read-only memory (hereinafter referred to as ROM) and a random access memory (hereinafter referred to as RAM).

The sensor input section 15 has two sensor input circuits that detect the temperature of the controlled object 14 and an A/D converter that converts the output into a digital signal, and the detailed configuration thereof is shown in FIG. 1. In this figure, a thermocouple input circuit 20 is an input circuit similar to the thermocouple bridge resistance circuit shown in FIG. 2, and provides an output corresponding to the thermoelectromotive force. That is, in the thermocouple input circuit 20, a resistor R1 and a cold junction compensation resistor R2 are connected to the power supply terminal, and further, resistors R3 and R4 are connected. The resistor R8 is a so-called burnout resistor having a high resistance value that maintains the output when the thermocouple 2 is damaged, and the thermocouple 2 is connected to the other ends of the resistor R1, the cold junction compensation resistor R2, and the burnout resistor R8. and resistance R3,
The midpoint of R4 is the analog switch 21a and the buffer circuit 22, such as a voltage follower. It is applied to the inverting input terminal of operational amplifier 23 via an input resistor. Similarly, the common connection point between the burnout resistor R8 and the thermocouple 2 is applied to the non-inverting input terminal of the power amplifier 23 via the analog switch 21b and the input resistor.

On the other hand, a platinum wire input circuit 24 using the platinum resistance wire 5 as a sensor is an input circuit similar to that shown in FIG. 3, and provides an output corresponding to the resistance value of the platinum resistance wire 5. That is, the platinum wire input circuit 24 includes a resistor R5, a platinum resistance wire 5, and resistors R6 and R7.
A bridge circuit is formed, the output of one end of which is connected to the buffer circuit 22 via an analog switch 25a, and the other end is provided to the non-inverting input terminal of the operational amplifier 23 via an analog switch 25b. Operational amplifier 23
is a differential amplifier circuit, which amplifies the potential difference from either sensor applied via an analog switch to A/
This is given to the D converter 26. Input selector switch 1
2 are analog switches 21a, 21b and 25a, 25
b is selectively made conductive, and the selection signal is given to the control section 17 at the same time as the analog switch.

The A/D converter 26 converts the applied signal into a digital signal at predetermined time intervals and provides the digital signal to the control section 17.

The control unit 17 is configured to perform processing such as realization of the input signal based on the switching signal of the input selector switch 12.
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In this way, the temperature regulator can be constructed by selectively using either a thermocouple or a platinum resistance wire sensor as an input sensor. The amplification factor of the operational amplifier 23 is determined by the input resistance at the inverting input terminal and the feed hack resistance, but since the buffer circuit 22 is provided at the output terminals of the analog switches 21a and 25a, the influence of the internal resistance is eliminated. The amplification factor can be determined only by the input resistance at the inverting input terminal.

In this embodiment, the analog switches 21a, 21b, 25a, and 25b are directly switched by the input changeover switch 12, but the output of the analog switch is
It is also possible to control each analog switch from the control section 7.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the configuration of a sensor input section of a temperature control device according to an embodiment of the present invention, Fig. 2 is a circuit diagram showing a thermocouple input circuit, and Fig. 3 is a circuit diagram showing a platinum wire input circuit. , FIG. 4 is a block diagram showing the overall configuration of the temperature control device of this embodiment. 10--Temperature control device I L--General regulator 12
---------Manual selection switch 15------Sensor input section 17---Control section 2 (1----
--Thermocouple input circuit 21a, 21b, 25a, 25
b--Analog switch 22-----Hasso circuit 23--Operation amplifier 24--One platinum wire input circuit 26--A/D converter patent applicant Tateishi Representative for Denki Co., Ltd. Patent attorney Kanki Okamoto (1 other person) W1 Figure 12--1------------------------------- −−−−−−−−−−−
−Ichigo Sosa Input Section 20−−−−−−−−−−−−−−−
- One ripe t7 size λ force route 21a, 21b, 25a, 25b
---1-7 size 0'7" 7+24--------
-----------Ippaku Heta Oiniri Town Approved Figure 2, 1 Figure 3

Claims (1)

[Claims] (1) A temperature control device that controls the temperature of a controlled object to a predetermined value, which includes a thermocouple input circuit that uses a thermocouple as a sensor and provides an output corresponding to the thermoelectromotive force, and a platinum resistance wire as a sensor and its resistance value. a sensor input section having a platinum wire input circuit that provides an output corresponding to the sensor input circuit; and an analog switch that is connected to the output ends of the thermocouple input circuit and the platinum wire input circuit and selectively switches the output; an input changeover switch means for supplying a switching signal for switching between the thermocouple input circuit and the platinum wire input circuit to the analog switch of the section; 1. A temperature control device, comprising: a control section that controls the temperature.