JPH0833776B2 - Temperature control device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a temperature control device characterized by the identification of a connected temperature sensor.

[Prior art and its problems]

(Prior Art) In a conventional temperature control device, a thermocouple, a platinum resistor, or the like is used as a temperature sensor. In the sensor input circuit 1 using a thermocouple, for example, as shown in FIG. 2, a bridge circuit is formed by a resistor R1, a cold junction compensation resistor R2 and resistors R3, R4, and a thermocouple 2 is connected to one end of the bridge circuit for calculation. It is amplified by the amplifier 3. Further, the sensor input circuit 4 using a platinum resistor has a bridge circuit formed by resistors R5, R6 and R7 including a platinum resistor 5 as shown in FIG. Is amplified by and is given as a voltage signal to an A / D converter (not shown).

(Problems to be Solved by the Invention) In such a conventional temperature controller, since the input circuit differs depending on the temperature sensor used, it is necessary to prepare a model having an input circuit corresponding to each input as the temperature controller. There was a problem that the number of models increased.

Therefore, it is conceivable to provide an input circuit that uses a thermocouple and a platinum resistor as sensors and switch them, but it is troublesome because the sensor input circuit must be switched by the temperature sensor connected to the temperature controller. There is a problem that it takes.

[Technical issues]

The present invention has been made in view of the above problems of the conventional temperature control device, and a sensor input circuit is provided in each temperature control device and the connected temperature sensors can be automatically identified. Is a technical issue.

[Constitution and effect of the invention]

(Means for Solving Problems) The present invention is a temperature adjusting device for controlling the temperature of a controlled object to a predetermined value, and as shown in FIG. 1, a thermocouple is used as a temperature sensor to cope with its thermoelectromotive force. A thermocouple input circuit for giving an output, a platinum resistor as a temperature sensor and a platinum resistor input circuit for giving an output corresponding to the resistance value, and a thermocouple input circuit and an output terminal of the platinum resistor input circuit respectively connected to A sensor input section having an analog switch for selectively switching the output, and an A / D converter connected to the sensor input section for converting the output of either the thermocouple input circuit or the platinum resistor input circuit into a digital value. , The temperature sensor to be connected is identified based on the fact that the A / D conversion output of the A / D converter obtained when the analog switch of the sensor input section is selectively switched is not the maximum value, and the control target is selected. Controlled to a predetermined temperature And a control unit for controlling.

(Operation) According to the present invention having such a feature, the temperature sensor is connected to the sensor input unit, the output thereof is selectively amplified through the analog switch, and the temperature sensor is connected to the control unit through the A / D converter. I am trying to enter. Therefore, in the thermocouple input circuit, when the thermocouple is not connected, the voltage of the reference voltage source of the thermocouple input circuit is A / D converted, and when the platinum resistor is not connected, the reference of the platinum resistor input circuit The value of the voltage source is A / D converted as it is. Therefore, the A / D conversion value becomes the maximum value. Therefore, it can be identified that the temperature sensor is connected to the input circuit that does not have the maximum value.

(Effect) Therefore, according to the present invention, since the single temperature control device has the sensor input section provided with each sensor input circuit, it is not necessary to prepare different temperature control devices for each temperature sensor, The number of models can be reduced and their management can be facilitated.

Also, the output of the sensor input section is A / D converted by the A / D converter and the connected temperature sensor can be automatically identified based on it, so the sensor input circuit is switched by the temperature sensor connected to the temperature control device. The effect is obtained that it is unnecessary and labor-free.

[Explanation of Example]

FIG. 4 is a block diagram showing the structure of the temperature control device according to the embodiment of the present invention. In this figure, the temperature control device 10
Is a setter 12 for setting the controlled variable of the controlled object 11, a display unit 13 for displaying the set value and the temperature of the controlled object 11, a temperature sensor 14 for detecting the temperature of the controlled object 11 such as a thermocouple or a platinum resistor. Is provided and a sensor input unit 15 for providing a voltage signal with respect to temperature is provided. Further, the temperature control device 10 includes an A / D converter 16 and a control unit 18 for converting an analog signal output from the sensor input unit 15 into a digital signal, and is connected to the control unit 18 including a heater and the like and controls the control target 11. Output part for direct control
19 are provided. The control unit 18 is composed of a central processing unit (hereinafter referred to as CPU), controls the control target 11 according to the control amount given from the sensor input unit 15, and identifies the type of the temperature sensor connected. The memory 17 is provided with a read-only memory (hereinafter referred to as ROM) that holds the processing procedure of the CPU and a random access memory (hereinafter referred to as RAM) that temporarily holds control data.

The sensor input section 15 has two sensor input circuits and an operational amplifier, as shown in the detailed structure of FIG.
In this figure, the thermocouple input circuit 20 is an input circuit similar to the bridge resistor circuit for thermocouple shown in FIG. 2, and provides an output corresponding to the thermoelectromotive force. That is, in the thermocouple input circuit 20, the resistance R1 and the cold junction compensation resistance R2 are connected to the voltage source end of the reference power supply Vref, and the resistances R3 and R4 are further connected. The resistor R8 is a so-called burnout resistor having a high resistance value that retains an output when the thermocouple 2 is damaged, and the thermocouple 2 is connected to the other end of the resistor R1, the cold junction compensation resistor R2 and the burnout resistor R8. . The variable resistor R9 is connected to the middle point of the resistors R3 and R4, and the reference voltage Vref at the point A is divided by the resistor R3, the variable resistor R9 and the resistor R4, and the buffer circuit such as the analog switch 21a and the voltage follower. 2
2, provided to the inverting input terminal of the operational amplifier 23 via the input resistor. Further, the common connection point between the burnout resistor R8 and the thermocouple 2 is similarly given to the non-inverting input terminal of the operational amplifier 23 via the analog switch 21b and the input resistor.

On the other hand, a platinum resistor input circuit using the platinum resistor 5 as a sensor
Reference numeral 24 is an input circuit similar to that shown in FIG. 3, which provides an output corresponding to the resistance value of the platinum resistor 5. That is, the platinum resistor input circuit 24 has a bridge circuit formed by the resistor R5, the platinum resistor 5, and the resistors R6 and R7 at the voltage source end of the reference power source Vref. The variable resistor R10 is connected to the middle point of the resistors R6 and R7, and the reference voltage Vref at the point B is divided by the resistors R6, R10 and R7. The voltage at the midpoint is given to the buffer circuit 22 via the analog switch 25a, and the outputs at the other ends are respectively fed to the operational amplifiers 23 via the analog switch 25b.
Applied to the non-inverting input of. The operational amplifier 23 is a differential amplifier circuit, which amplifies the potential difference from one of the sensors given via the analog switch and gives it to the A / D converter 16. Here, the reference voltage Vref is the A / D converter 16
A voltage sufficiently higher than the linear input voltage range of is selected, and the reference voltage source is also given to the A / D converter 16 as necessary. The A / D converter 16 converts the supplied analog input voltage into a digital signal at predetermined time intervals and supplies the digital signal to the control unit 18.

Here, the temperature sensor identification processing will be described with reference to the flowchart shown in FIG. When the power is turned on, the operation is started. First, in step 31, the analog switches 21a and 21b are made conductive, and the analog switches 25a and 25b are set in the insulating state to connect the thermocouple input circuit 20 to the operational amplifier 23. Then, proceed to step 32 and A / D converter 16 at that time
Check whether the A / D conversion value of the reference voltage source of is the maximum value. At this time, if the thermocouple 2 is not connected, the voltage at the non-inverting input terminal of the operational amplifier 23 of the thermocouple input circuit 20 becomes substantially the same level as the reference power supply Vref at point A in FIG. The voltage Vout becomes a saturation value.
Therefore, if this value is A / D converted by the A / D converter 16,
It is the maximum value of D converter 16. If the A / D conversion value is not the maximum, the routine proceeds to step 33, where it is recognized that the thermocouple 2 is connected.

If the A / D conversion value is the maximum, the thermocouple 2 is not connected, so proceed to step 34 to make the analog switches 21a and 21b in an isolated state to make the analog switches 25a and 25b conductive and calculate the platinum resistor input circuit 24. Connect to amplifier 23. Then, the process proceeds to step 35, and it is checked whether the A / D conversion value of the reference voltage source of the platinum resistor input circuit 24 is the maximum value. When the platinum resistor 5 is not connected, both the non-inverting input terminal and the inverting input terminal of the operational amplifier 23 are Vref at point B in FIG.
Therefore, the output voltage Vout becomes equal to the reference voltage Vref. At this time, the reference voltage Vref is set higher than the linear input range of the A / D converter 16, so the reference voltage
If Vref is A / D converted, it also becomes the maximum value of A / D conversion.
Therefore, if the A / D conversion value is not the maximum, the routine proceeds to step 36, where it is recognized that the platinum resistor 5 is connected. This A /
If the D conversion value is the maximum, neither the thermocouple 2 nor the platinum resistor 5 is connected, so the operation is stopped. Step
After it is confirmed in 33 and 36 that the thermocouple 2 or the platinum resistor 5 is connected, the routine proceeds to a routine 37 to start the temperature control operation.

By doing this, the thermocouple 2 and the platinum resistor 5 serve as temperature sensors.
It is possible to configure a temperature adjusting device that selectively uses any one of the temperature sensors, and it is possible to automatically recognize the temperature sensor connected to the temperature adjusting device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a sensor input section of a temperature controller 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 showing a platinum resistor input circuit. FIG. 4 and FIG. 4 are block diagrams showing the overall configuration of the temperature adjusting device of this embodiment, and FIG. 5 is a flowchart showing the temperature sensor identification processing. 2 ... Thermocouple, 5 ... Platinum resistor, 10 ... Temperature controller, 14 ... Temperature sensor, 15 ... Sensor input section, 16 ... A /
D converter, 18 ... Control unit, 20 ... Thermocouple input circuit, 21a, 2
1b, 25a, 25b …… Analog switch, 23 …… Operational amplifier,
24 …… Platinum resistor input circuit

Claims (1)

[Claims] 1. A temperature adjusting device for controlling the temperature of a controlled object to a predetermined value, wherein a thermocouple is a temperature sensor, a thermocouple input circuit for giving an output corresponding to its thermoelectromotive force, and a platinum resistor is a temperature sensor. A platinum resistor input circuit that provides an output corresponding to the resistance value, and a sensor input unit having an analog switch that is respectively connected to the thermocouple input circuit and the output ends of the platinum resistor input circuit and that selectively switches the output, An A / D converter that is connected to the sensor input unit and converts the output of either the thermocouple input circuit or the platinum resistor input circuit into a digital value, and the analog switch of the sensor input unit is selectively switched. When the A / D conversion output of the A / D converter obtained at the time identifies the connected temperature sensor based on the fact that it is not the maximum value, and a control unit for controlling the controlled object to a predetermined temperature, Temperature regulating device according to claim.