JP2004279171A - Input circuit and measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an input circuit permitting the input from a thermocouple, a temperature measuring resistor, a voltage output sensor, and a current output sensor, without increasing the number of input terminals, and also to provide a measurement apparatus having the same. <P>SOLUTION: The connection of the first and the second input terminals 6 and 7 among the first-third input terminals 6-8 to which either of the thermocouple 2, the temperature measuring resistor 3, the current output sensor 4, and the voltage output sensor 5 is selectively connected is switched by the interlocked switching operation of a slide switch 16 having a first-third switch parts 16-1 to 16-3, so that the thermocouple 2, the temperature measuring resistor 3, the current output sensor 4, and the voltage output sensor 5 are connected to corresponding analog input lines. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an input circuit to which an analog signal from a temperature sensor or another sensor is input, and a measuring instrument including the input circuit, and more particularly, to a thermocouple, a resistance temperature detector, a current or voltage output The present invention relates to an input circuit capable of inputting an analog signal from a sensor and a measuring device including the input circuit for measuring temperature and other physical quantities.
[0002]
[Prior art]
Generally, in an input circuit to which both a thermocouple and a resistance temperature detector can be connected, three input terminals are required because the resistance temperature detector has three terminals (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-5-296853
[Problems to be solved by the invention]
In addition to temperature measurement with thermocouples and resistance thermometers, for example, when trying to measure other physical quantities such as pressure and flow rate, it is necessary to input current and voltage from current output sensors and voltage output sensors. , And four input terminals.
[0005]
However, when four terminals are used, the number of terminals is increased and the whole becomes large as compared with the case of three terminals, so that the measurement device cannot be reduced in size and thickness.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made without increasing the number of input terminals, and without any trouble for a user, and a thermocouple, a resistance temperature detector, a voltage output sensor, and a current output. An object of the present invention is to provide an input circuit capable of inputting an analog signal from a sensor and a measuring device including the input circuit.
[0007]
[Means for Solving the Problems]
The present invention has the following configuration to achieve the above object.
[0008]
That is, the input circuit of the present invention is an input circuit that can selectively connect any one of a thermocouple, a resistance temperature detector, a current output sensor, and a voltage output sensor, and includes first to third input terminals. There is provided switching means for switching and connecting the input terminal to analog input lines corresponding to the thermocouple, the resistance temperature detector, the current output sensor, and the voltage output sensor.
[0009]
According to the present invention, there is provided switching means for switching and connecting the input from the three input terminals to the analog input lines corresponding to the thermocouple, the resistance temperature detector, the current output sensor and the voltage output sensor. Temperature and other measurements can be made without increasing the number.
[0010]
In one embodiment of the present invention, the switching means includes a switch operated to be switched, and the switch connects the first and second input terminals to a thermocouple, a resistance thermometer, a current output sensor, and a voltage. The four types of output sensors are divided into two sets of two types of sensors, and are switched in connection with an analog input line corresponding to one set of sensors or an analog input line corresponding to the other set of sensors. is there.
[0011]
According to the present invention, by operating the switch, the first and second input terminals are connected to two sets of two types each of four types of sensors of a thermocouple, a resistance temperature detector, a current output sensor, and a voltage output sensor. The analog input line corresponding to one set of sensors divided into the sensors or the analog input line corresponding to the other set of sensors can be switched and connected in conjunction with the analog input line corresponding to the other set of sensors. It is preferable to use a relatively low thermocouple and a resistance temperature detector, and to use the other set of sensors as a current output sensor and a voltage output sensor that have relatively high input voltages.
[0012]
In another embodiment of the present invention, the thermocouple is connected between second and third input terminals, and the resistance thermometer is connected to the first, second, and third input terminals. , The current output sensor is connected between first and third input terminals, the voltage output sensor is connected between second and third input terminals, and the switches are interlocked. A slide switch having first to third switch units to be switched and connected, wherein the first switch unit has a first input terminal connected to an analog input line corresponding to a resistance temperature detector or an analog input line corresponding to a current output sensor. A second switch unit switches and connects to a first analog relay line that is a part of an input line, and a second switch unit connects a second input terminal to a second analog relay line that is a part of an analog input line corresponding to a thermocouple. Line or voltage And switching connected to the analog input line corresponding to the force sensor, the third switch section, the first, the second analog relay line is for switching connected to a corresponding analog input line.
[0013]
According to the present invention, the input terminal and the internal analog relay line are switched and connected by the switching operation of the slide switch having the first to third switch portions, and the thermocouple, the resistance temperature detector, It can be connected to the analog input lines respectively corresponding to the current output sensor and the voltage output sensor.
[0014]
A measuring instrument of the present invention includes the input circuit of the present invention, and an A / D converter for A / D converting an analog signal from the analog input line of the input circuit, wherein the thermocouple or the resistance temperature detector is used. At least the temperature is measured based on the analog signal from.
[0015]
Here, the measuring device is a device that measures temperature and other physical quantities, and may be a device having a measuring function, and includes an adjusting device that measures and controls based on the measured function.
[0016]
According to the present invention, temperature and other physical quantities can be measured based on analog inputs from thermocouples, resistance temperature detectors, current output sensors, and voltage output sensors without increasing the number of input terminals. The size and thickness of the device can be reduced.
[0017]
In a preferred embodiment of the present invention, at least two A / D converters are provided, and one of the A / D converters converts an analog signal from a thermocouple into an analog signal while the other converts the analog signal from the thermocouple. The A / D converter converts the analog signal from the temperature sensing element for compensating for the cold junction.
[0018]
According to the present invention, analog inputs from a thermocouple and a temperature-sensitive element are respectively supplied to each A / D converter. Accurate temperature measurement becomes possible.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0020]
(Embodiment 1)
FIG. 1 is a block diagram of a measuring device such as a controller according to one embodiment of the present invention.
[0021]
The measuring device 1 according to the present embodiment measures temperature and other physical quantities such as pressure and flow rate and controls them to be a target value, and outputs a thermocouple 2, a resistance thermometer 3, and a direct current. One of the current output sensor 4 and the voltage output sensor 5 that outputs a DC voltage is selectively connected, and includes first to third input terminals 6 to 8.
[0022]
The thermocouple 2 is connected between the second input terminal 7 and a third input terminal 8 serving as a ground, and the resistance temperature detector 3 is a three-wire type, Are connected to the input terminals 6 to 8. The current output sensor 4 is connected between the first and third input terminals 6 and 8, and the voltage output sensor 5 is connected between the second and third input terminals 7 and 8.
[0023]
The measuring device 1 of this embodiment includes an input circuit 9 to which analog inputs from the thermocouple 2, the resistance temperature detector 3, the current output sensor 4, and the voltage output sensor 5 are provided, and an analog input from the input circuit 9. A first and second two A / D converters 10 and 11 for A / D conversion, a CPU 12 for performing measurement processing, PID control, and the like based on the outputs of these A / D converters 10 and 11; A setting unit 13 for inputting various settings such as a setting value, a display unit 14 for displaying measured values and target values, and an output unit 15 for outputting a control output and the like are provided.
[0024]
The input circuit 9 includes a three-pole slide switch 16 and first to fourth analog switches 17 controlled by the CPU 12 as switching means for switching and connecting the first and second input terminals 6 and 7 as described later. To 20.
[0025]
The slide switch 16 has first to third switch units 16-1 to 16-3 that are switched in conjunction with each other by a switching operation. Each of the switch units 16-1 to 16-3 includes a movable contact 21-. 1 to 21-3, and first and second fixed contacts 22-1 to 22-3 and 23-1 to 23-3, respectively.
[0026]
The movable contacts 21-1 and 21-2 of the first and second switch sections 16-1 and 16-2 are connected to the first and second input terminals 6 and 7, respectively. The movable contact 21-3 of the section 16-3 is connected to the second A / D converter 11 via an analog input line 38 for measuring the resistance of the lead 3 of the resistance temperature detector 3, and is connected to the third A / D converter 11. It is connected to the first A / D converter 10 via an analog switch 19.
[0027]
Further, the second fixed contact 23-1 of the first switch unit 16-1 and the second fixed contact 23-3 of the third switch unit 16-3 are connected by the first analog relay line 24. The first fixed contact 22-2 of the second switch unit 16-2 and the second fixed contact 22-3 of the third switch unit 16-3 are connected to the second analog relay line 25. Connected.
[0028]
The first analog relay line 24 constitutes a part of an analog input line of the current output sensor 4 as described later, and the second analog relay line 25 is connected to the thermocouple 2 as described later. It constitutes a part of the analog input line and also constitutes a part of the analog input line for measuring the lead resistance of the resistance bulb 3. The first analog relay line 24 is provided with voltage dividing resistors 29 and 30, and the second analog relay line 25 is provided with a resistor 31.
[0029]
The first fixed contact 22-1 of the first switch section 16-1 is connected to the analog input line 26 corresponding to the resistance temperature detector of the first A / D converter 10, and the second switch The second fixed contact 23-2 of the unit 16-2 is connected to an analog input line corresponding to the thermocouple, the voltage output sensor, and the current output sensor of the first A / D converter 10 via the fourth analog switch 20. 27. Voltage dividing resistors 32 and 33 are interposed between the second fixed contact 23-2 and the fourth analog switch 20.
[0030]
The analog input line 26 and the second analog relay line 25 corresponding to the resistance temperature detector are connected to the power supply via the resistors 34 and 35 and the first analog switch 17, respectively. Reference numeral 25 is connected to a power supply via a resistor 36 and the second analog switch 18.
[0031]
One end of a cold-sensing compensation temperature sensing element 28 is connected to the second A / D converter 11 via an analog input line 39, and this one end is connected to a power supply via a resistor 37. I have.
[0032]
The operation of the measuring device 1 having the above configuration will be described for each case where the thermocouple 2, the resistance temperature detector 3, the current output sensor 4, and the voltage output sensor 5 are connected.
[0033]
(1) Resistance temperature detector When the resistance temperature detector 3 is connected to the first to third input terminals 6 to 8 and the slide switch 16 is slid to the temperature measurement side, the switching connection state shown in FIG. The CPU 12 turns on only the first analog switch 17 based on a setting input from the setting unit 13 indicating that the resistance bulb 3 is connected.
[0034]
Thus, a current for temperature measurement is supplied to the resistance thermometer 3 via the first analog switch 17, and an analog input from the resistance thermometer 3 is supplied to the first input terminal 6 and the first input terminal 6. While being supplied to the first A / D converter 10 via the switch section 16-1 and the analog input line 26, the analog input corresponding to the conductor resistance is supplied to the second input terminal 7, the second switch section 16- 2, to the second A / D converter 11 via the second analog relay line 25, the third switch section 16-3, and the analog input line 38.
[0035]
The analog input given to each of the A / D converters 10 and 11 is converted into a digital signal and given to the CPU 12, and the CPU 12 cancels the wire resistance and converts it into temperature data, and displays the measured temperature on the display unit. 14 and a control output is given so as to reach the target temperature.
[0036]
(2) Thermocouple When the thermocouple 2 is connected between the second and third input terminals 7 and 8 and the slide switch 16 is slid to the temperature measurement side, a switching connection state shown in FIG. The CPU 12 turns on the second and third analog switches 18 and 19 based on the setting input from the setting unit 13 indicating that the thermocouple 2 is connected. The connection state of the first to third switch sections 16-1 to 16-3 of the slide switch 16 is the same as that in FIG.
[0037]
In this state, the analog input from the thermocouple 2 is supplied to the second input terminal 7, the second switch section 16-2, the second analog relay line 25, the third switch section 16-3, and the third analog section. While being supplied to the first A / D converter 10 via the switch 19 and the analog input line 27, the analog input from the temperature-sensitive element 28 is supplied to the second A / D converter 11 via the analog input line 39. Given to.
[0038]
The analog input given to each of the A / D converters 10 and 11 is converted into a digital signal and given to the CPU 12, which converts the temperature into temperature data and displays the temperature measured by performing the cold junction compensation. In addition to the display on the unit 14, a control output is given so as to reach the target temperature.
[0039]
The reason why the second analog switch 18 is turned on is that when the thermocouple 2 is disconnected due to deterioration or the like, a high voltage is input and the disconnection can be detected.
[0040]
Thus, the first and second A / D converters 10 and 11 are provided, and the analog inputs from the thermocouple 2 and the temperature-sensitive element 28 are supplied to the respective A / D converters 10 and 11 respectively. Therefore, high-speed and high-accuracy temperature measurement can be performed as compared with a configuration in which switching is provided to one A / D converter.
[0041]
(3) Current output sensor When the current output sensor 4 is connected between the first and third input terminals 6 and 8 and the slide switch 16 is slid to another measurement side other than the temperature measurement, the slide switch 16 The first to third switch sections 16-1 to 16-3 are switched in an interlocked manner to be in the switching connection state shown in FIG. 4, and the CPU 12 is connected to the current output sensor 4 from the setting section 13. Only the third analog switch 19 is turned on based on the setting input indicating that the setting has been completed.
[0042]
As a result, the analog input from the current output sensor 4 is transmitted to the first input terminal 6, the first switch unit 16-1, the first analog relay line 24, the third switch unit 16-3, and the third analog terminal. The signal is supplied to the first A / D converter 10 via the switch 19 and the analog input line 27 to be converted into a digital signal, further supplied to the CPU 12 and converted into corresponding measurement data. , And the CPU 12 gives a control output so as to reach the target value.
[0043]
(4) Voltage output sensor When the voltage output sensor 5 is connected between the second and third input terminals 7 and 8, and the slide switch 16 is slid to the other measurement side other than the temperature measurement, it is shown in FIG. The CPU 12 turns on only the fourth analog switch 20 based on a setting input from the setting unit 13 indicating that the voltage output sensor 5 is connected.
The connection state of the first to third switch sections 16-1 to 16-3 of the slide switch 16 is the same as that of FIG.
[0044]
In this state, the analog input from the voltage output sensor 5 is supplied to the first A / D via the second input terminal 7, the second switch section 16-2, the fourth analog switch 20, and the analog input line 27. The signal is supplied to the converter 10 and converted into a digital signal. The signal is further supplied to the CPU 12 and converted into corresponding measurement data. The measurement data is displayed on the display unit 14 and the CPU 12 controls the target value. Give output.
[0045]
As described above, the inputs of the thermocouple 2, the resistance temperature detector 3, the current output sensor 4, and the voltage output sensor 5 can be measured by the first to third three input terminals 6 to 8. It is not necessary to increase the number, and the measuring instruments can be reduced in size and thickness.
[0046]
In this embodiment, the slide switch 16 switches between temperature measurement by the thermocouple 2 and the resistance temperature detector 3 and other measurements by the current output sensor 4 and the voltage output sensor 5, that is, the input voltage. Switches the analog input line between a relatively low temperature measurement and another measurement with a relatively high input voltage, so that the thermocouple 2 or the resistance temperature detector 3 may be incorrectly connected during temperature measurement, or In other measurements, even if the current output sensor 4 or the voltage output sensor 5 is erroneously connected, it is possible to prevent the internal circuit elements and the like from being broken.
[0047]
(Other embodiments)
As another embodiment of the present invention, the number of A / D converters may be increased to reduce the number of analog switches.
[0048]
Although the above embodiment has been described by applying the present invention to a controller, the present invention can be similarly applied to a digital panel meter for measuring physical quantities such as temperature, pressure, and flow rate as another embodiment of the present invention. is there.
[0049]
【The invention's effect】
As described above, according to the present invention, switching means for switching and connecting the input from the three input terminals to the analog input lines corresponding to the thermocouple, the resistance temperature detector, the current output sensor, and the voltage output sensor is provided. Therefore, temperature and other measurements can be performed without increasing the number of input terminals, and the size and thickness of the measurement device can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a measuring device according to one embodiment of the present invention.
FIG. 2 is a block diagram showing a state where a resistance bulb is connected.
FIG. 3 is a block diagram showing a state where a thermocouple is connected.
FIG. 4 is a block diagram showing a state where a current output sensor is connected.
FIG. 5 is a block diagram showing a state where a voltage output sensor is connected.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Measuring device 2 Thermocouple 3 Resistance temperature detector 4 Current output sensor 5 Voltage output sensor 6-8 First to third input terminals 10, 11 First and second A / D converter 16 Slide switch 16-1 16-3 First to third switch units 24 and 25 First and second analog relay lines

Claims (6)

An input circuit including a thermocouple, a resistance temperature detector, a current output sensor, and a voltage output sensor that can be selectively connected to each other, and including first to third three input terminals,
An input circuit, further comprising switching means for switching and connecting the input terminal to analog input lines corresponding to the thermocouple, the resistance temperature detector, the current output sensor, and the voltage output sensor. The switching means includes a switch operated to be switched,
The switch is configured to divide the first and second input terminals into two sets of two types each of four types of sensors of a thermocouple, a resistance temperature detector, a current output sensor, and a voltage output sensor. 2. The input circuit according to claim 1, wherein the switching circuit is switched in connection with an analog input line corresponding to the sensor or an analog input line corresponding to the other set of sensors. 3. The input circuit according to claim 2, wherein the one set of sensors is the thermocouple and the resistance temperature sensor, and the other set of sensors is the current output sensor and the voltage output sensor. The thermocouple is connected between second and third input terminals, the resistance thermometer is connected to the first, second, and third input terminals, and the current output sensor is connected to first and second input terminals. A voltage output sensor connected between a third input terminal and the voltage output sensor connected between the second and third input terminals;
The switch is a slide switch having first to third switch units that are switched and connected in conjunction with each other,
A first switch unit that switches and connects the first input terminal to a first analog relay line that is a part of an analog input line corresponding to the resistance temperature detector or an analog input line corresponding to the current output sensor; The second switch unit switches and connects the second input terminal to a second analog relay line or an analog input line corresponding to a voltage output sensor, which is a part of the analog input line corresponding to the thermocouple. 4. The input circuit according to claim 3, wherein the switch section switches the first and second analog relay lines to corresponding analog input lines. An input circuit according to any one of claims 1 to 4, and an A / D converter for A / D converting an analog signal from the analog input line of the input circuit, wherein the thermocouple or the resistance temperature detector is provided. A measuring device for measuring at least temperature based on an analog signal from a body. At least two A / D converters are provided. One of the A / D converters converts an analog signal from a thermocouple into an analog signal, and the other A / D converter provides a sensor for cold junction compensation. 6. The measuring device according to claim 5, wherein the analog signal from the temperature element is A / D converted.

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