JPH05134701A - Signal input/output device - Google Patents

Abstract

PURPOSE:To use almost all circuit elements in common and to change a circuit dedicated to inputting and circuit dedicated to outputting with a simple operation by providing a regulator which is constituted so as to be possibler to be operated in both constant current and constant voltage modes and a means for changing-over the mode of the regulator in accordance with the kinds of field equipments connected with an external terminal. CONSTITUTION:A mode setting means 14 connects a switch SW with a contact S1 side at the time of operating as the input circuit. Thus, partial pressure voltages by partial pressure resistors R1 and R2 are fed-back to one input end(-) of an amplifier A1 constituting the regulator 12 and the regulator 12 becomes the constant voltage output mode. The mode setting means 14 connects the switch SW with the contact S2 side at the time of operating as the output circuit. Thus, the register R which constitutes a current signal receiving means 11 is connected with the one input end(-) of the amplifier A1 constituting the regulator so as to be a feed-back resistor and the regulator 12 becomes the constant current output mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal input / output device used for process control and the like, and more specifically, it receives a process signal from a sensor installed in a process,
The present invention relates to a signal input / output device for outputting a drive signal for driving various actuators installed in a process.

[0002]

2. Description of the Related Art In process industries such as petroleum refining, petrochemicals, steelmaking and papermaking, control devices using computers are used for controlling various process amounts such as temperature, flow rate, pressure and liquid level. This control device receives signals related to process amounts such as temperature, flow rate, pressure, and liquid level from various sensors installed in each part of the plant, and the actuators (for example, valves) installed in the plant are connected to the actuators. A drive signal for driving is output. FIG. 7 is a structural conceptual diagram showing a relationship between a control device for controlling such a plant and sensors or transmitters and actuators installed in respective parts of the plant. In the figure, 1
Is a control device composed of a computer and has, for example, a PID control calculation function and a sequence control function. Reference numeral 2 is an input signal conversion circuit for inputting process signals from various sensors or transmitters 3 and converting it into a signal of, for example, 1 to 5 V which is easy to handle in the apparatus. Reference numeral 4 is a digital signal which can be processed by a computer. A / convert to signal
It is a D converter. Reference numeral 5 is a D / A converter for converting a digital signal output from the control device 1 into an analog signal, and 6 is an actuator 7 for converting the analog signal from the D / A converter 5.
Is an output signal conversion circuit for converting into a drive signal for driving the. Here, the input signal conversion circuit 2 and the output signal conversion circuit 6 are collectively referred to as a signal conditioner. FIG. 8 is a configuration block diagram showing an example of a conventional input signal conversion circuit 2. Here, the circuit assumes a sensor or transmitter connected via a two-wire transmission path 8. Es is transmitter 3
For example, 24V is supplied as a power supply for operating the side. The transmitter 3 outputs a current signal Ip of, for example, 4 to 20 mA to the transmission line 8 according to the detected process amount. The resistance Ri inserted in the transmission line 8 generates a voltage signal Vi corresponding to the transmitted current Ip, and the voltage / pulse width converter VPW converts this voltage signal into a pulse width signal and applies it to the photocoupler PC. Signal isolation. The pulse width signal from the photo coupler PC is converted into a voltage signal again by the pulse width / voltage converter PWV,
It is converted into voltage signals OUT1 and OUT2 of, for example, 1 to 5 V which are easy to handle in the device through the amplifier A1 or the amplifier A2. FIG. 9 is a configuration block diagram showing an example of a conventional output signal conversion circuit 6. The signal output from the inside of the device is applied to the current control transistor Qo via the amplifiers A3 and A4 after being signal-insulated, and here, for example, 4 to
The drive current signal Io of 20 mA is converted and transmitted to the actuator (load) 7.

[0003]

The conventional signal converters 2 and 6 used in the control device are classified into those which handle an input signal and those which handle an output signal as shown in FIG. 8 and FIG. Different items are prepared due to different configurations. The present invention has been made in view of the above circumstances, and an object thereof is to use almost all constituent elements in common and to handle an input signal from a process and an output circuit to output a driving signal or the like to the process. It is an object of the present invention to provide a signal input / output device that can be changed by simple operation.

[0004]

The present invention which achieves such an object is to provide at least a pair of external terminals to which a transmission line is connected, current signal receiving means for receiving a current flowing through the transmission line, and the external device. Depending on the type of the field device connected to the external terminal and the regulator configured to operate in both the constant current mode that outputs a constant current to the terminal and the constant voltage mode that outputs a constant voltage to the external terminal. A mode switching means for switching the regulator to a constant voltage mode or a constant current mode is provided.

[0005]

When the current signal is input from the process, the mode switching circuit switches the regulator to the constant voltage mode and takes out the signal sent from the process via the current signal receiving means. When outputting a current signal as an actuator drive signal to the process, the mode switching circuit switches the regulator to the constant current mode and controls the regulator with a signal to be transmitted. By switching and setting the operation mode of the regulator in this way, a signal input circuit and a signal output circuit are realized with substantially the same configuration.

[0006]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of the present invention. In the figure, T1 and T2 are a pair of external terminals to which a transmission line (not shown) is connected, and 11 is a current signal receiving means for receiving a current flowing through the transmission line, that is, a current flowing through a pair of terminals T1 and T2. In this embodiment, the terminal T1
A resistor R is connected between the ground and the ground, and a signal due to the voltage drop is taken out as a received signal. An element other than a resistor may be used as the signal receiving means. Reference numeral 12 is a regulator configured to operate in both a constant current mode in which a constant current is output to the external terminals T1 and T2 and a constant voltage mode in which a constant voltage is output to the external terminals. The collector has a DC power supply Vcc. Connected to the
Transistor Q1 whose emitter is connected to external terminal T1
And an amplifier A1 whose output end is connected to the emitter of the transistor Q1. 13 is an external terminal T
1 and T2 is a mode switching circuit that switches the regulator 12 to a constant voltage mode or a constant current mode according to the type of field device connected to the switch SW, and connects the switch SW to one of the contacts S1 and S2. A signal output unit 1 for applying or not applying a signal having a predetermined magnitude to one input terminal (+) of the amplifier A1 according to the setting unit 14 to be set and the mode setting in the setting unit 14.
It is composed of 5. As the signal output means 15,
For example, a D / A converter is used.

R1 and R2 are voltage dividing resistors connected between the terminal T1 and the ground, SR is a signal take-out terminal for taking out a signal received by the current signal receiving means 11, and SS is a regulator 1.
2 is connected to one input terminal (+) of the amplifier A1 constituting
It is a signal application terminal that gives a signal to be transmitted. The signal to be transmitted here corresponds to, for example, a signal output from the control output calculated by the control device via the D / A converter. In this case, this D / A converter is used as the signal output means 1
It may also be used for 5. The common terminal of the switch SW is connected to the other input terminal (-) of the amplifier A1, the contact S1 is connected to the common connection point of the voltage dividing resistors R1 and R2, and the contact S is also connected.
Reference numeral 2 is connected to one end of a resistor R which constitutes the current signal receiving means 11. This switch SW is the setting means 1
4, the regulator 12 is in a constant voltage output mode by using the voltage dividing resistors R1 and R2 as feedback resistors, and is also in a constant current output mode by using the resistor R as a feedback resistor. Has been done.

Next, the operation of the device thus constructed is operated as an input circuit for inputting a signal from a transmitter or a sensor installed in the process, and as an output circuit for outputting a drive signal to an actuator installed in the process. A description will be given separately for the case of operating. (When inputting current signal from process; operation as input circuit) FIG. 2 is a diagram showing a connection state in this case.
Between the external terminals T1 and T2, for example, a transmitter 3 that outputs a current signal is connected as a field device via the transmission line 8. The mode setting means 14
The switch SW is connected to the contact S1 side. As a result, the divided voltage by the voltage dividing resistors R1 and R2 is fed back to one input terminal (−) of the amplifier A1 that constitutes the regulator 12, and the regulator 12 enters the constant voltage output mode. Further, the signal output means 15 applies a predetermined voltage signal Vi to the other input terminal (+) of the amplifier A1. This allows
The regulator 12 controls so that the output voltage Vout output between the external terminal T1 and the ground is maintained at a constant voltage of, for example, 24 V corresponding to the predetermined voltage signal Vi. That is, the output voltage Vout output to the terminal T1
Vout = Vi / β where β is represented by a resistance division ratio determined by the resistance R and the voltage dividing resistances R1 and R2. The transmitter 3 controls the current Iin flowing through the transmission line 8 according to the process amount,
Transmit process signals. The process signal (current Iin) transmitted via the transmission line 8 is the current signal receiving means 11
Flowing through the resistor R that forms the voltage Eout, and generates a voltage Eout corresponding to the amount of process occurring across the resistor R. This voltage signal is taken out from the reception signal taking-out terminal SR. This signal voltage Eout is expressed by Eout = Iin × R. Such a received signal obtained at the terminal SR is
It is sent to an A / D converter (not shown).

(When a current signal is output to the process as an actuator drive signal; it operates as an output circuit)
FIG. 3 is a diagram showing a connection state in this case. External terminal T1,
Actuator (load) via T8 between T2
7 is connected. The mode setting means 14 is a switch SW
Is connected to the contact S2 side. As a result, the regulator 1
2 is connected to one input terminal (−) of the amplifier A1 which constitutes
The resistor R that constitutes the current signal receiving means 11 is connected so as to serve as a feedback resistor, and the regulator 12 enters the constant current output mode. Further, in this state, the signal Vs to be output to the process is applied to the terminal SS connected to the other input terminal (+) of the amplifier A1. As a result, the regulator 12 outputs the signal from the external terminal T1 to the process. The output current Iout to be transmitted is controlled according to the signal Vs. Terminal T
Output current Iout transmitted from 1 to the process
Is represented by Iout = Vs / R.

As described above, the constituent elements of the main part can be shared when operating as an input circuit for inputting a signal from a process and when operating as an output circuit for outputting a drive signal to the process. In addition, it is possible to switch between the case of operating as an input circuit and the case of operating as an output circuit by a simple operation in the mode switching circuit 13.

As field devices, there are transmitters and sensors that output voltage signals in addition to the current signals described in FIGS. 2 and 3. There are also actuators that are driven by voltage signals. Next, a case where the present invention is applied to a field device that handles these voltage signals will be described. (When a voltage signal is input from the process; operates as an input circuit) FIG. 4 is a diagram showing a connection state in this case.
A transmitter 3 such as a potentiometer that outputs a voltage signal Vp is connected between the external terminals T1 and T2 via a transmission line 8 as a field device. The mode setting means 14 connects the switch SW to the contact S2 side. As a result, the current signal receiving means 11 is connected to one input terminal (-) of the amplifier A1 that constitutes the regulator 12.
Is connected so that the resistor R constituting the above becomes a feedback resistor. Further, the signal V from the signal output means 15 to the other input terminal (+) of the amplifier A1 for keeping the regulator 12 in the cutoff mode or the minute current output mode.
Apply io. As a result, the voltage signal Vp sent from the transmitter 3 side via the transmission path 8 appears as Vout at the pair of external terminals T1 and T2. This voltage signal Vout is taken out from the terminal SRV connected to the external terminal T1. The signal Vout taken out from the terminal SRV is: Vp = Vout / β where β is converted into the voltage signal Vp sent from the process by calculating the resistance voltage dividing ratio determined by the resistor R and the voltage dividing resistors R1 and R2. be able to.

(When a voltage signal is output to the process as an actuator drive signal; it operates as an output circuit)
FIG. 3 is a diagram showing a connection state in this case. External terminal T1,
An actuator (load) 7 that operates with a voltage signal is connected between T2 via a transmission line 8. Mode setting means 1
4 connects the switch SW to the contact S1 side. As a result, the divided voltage by the voltage dividing resistors R1 and R2 is fed back to one input terminal (−) of the amplifier A1 that constitutes the regulator 12, and the regulator 12 enters the constant voltage output mode. Further, the signal Vs to be output to the process is applied to the terminal SS connected to the other input terminal (+) of the amplifier A1, whereby the regulator 12 outputs the output voltage output from the external terminal T1 to the process. Vout is signal V
Control according to s. The output voltage Vout output from the terminal T1 to the process is represented by Vout = Vs / β. Note that, here, it is assumed that the voltage division ratio of the resistor R is ignored, but if this cannot be ignored, FIG.
, The voltage signal obtained across the resistor R is applied to the terminal SR.
Then, the value of the signal Vs applied to the other input terminal (+) of the amplifier A1 may be corrected. Further, in place of the external terminal T2, another external terminal T3 connected to the ground is provided, and the connection of the transmission line 8 line is performed by the external terminal T2.
May be changed to the external terminal T3. As described above, the device of the present invention has the same circuit configuration when handling a voltage signal, and the operation as an input circuit and the operation as an output circuit can be switched by a simple operation by the setting means.

FIG. 6 is a block diagram showing the configuration of another embodiment of the present invention. In this embodiment, the resistor R serves as a feedback resistor, the amplifier A2 having one input terminal (+) connected to the ground, and the voltage dividing resistor R2 serve as a feedback resistor, and one input terminal (+) serves as a feedback resistor. The amplifiers A3 connected to the ground are provided respectively. In this embodiment, one ends of the resistors R and R2 connected to the other input ends (-) of the amplifiers A2 and A3 can be set to virtual ground, respectively.
It is possible to eliminate the influence of partial pressure due to these resistances.

In each of the above embodiments, the DC power supply Vcc connected to the regulator 12 may be supplied from outside the device. Also, the signal output means 15 connected to one input terminal (+) of the amplifier A1 may be shared with the one that outputs the signal Vs to be transmitted to the process side when the device is operated as an output circuit. Good. Further, the mode switching circuit 13 may be realized by software.

[0015]

As described above in detail, according to the present invention, most of the circuit elements are common to the input-only circuit for inputting the signal from the process and the output-only circuit for outputting the signal to the process. It is possible to switch to either circuit by a simple mode setting operation. Therefore, the input / output circuits can be integrated into one type, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a connection state when a current signal is input from a process (when operating as an input circuit).

FIG. 3 is a diagram showing a connection state when a current signal is output to the process as an actuator drive signal (when it operates as an output circuit).

FIG. 4 is a diagram showing a connection state when a voltage signal is input from a process (when it operates as an input circuit).

FIG. 5 is a diagram showing a connection state when a voltage signal is output to the process as an actuator drive signal (when it operates as an output circuit).

FIG. 6 is a configuration block diagram showing another embodiment of the present invention.

FIG. 7 is a structural conceptual diagram showing a relationship between a control device for controlling a plant and a sensor or a transmitter or an actuator installed in each part of the plant.

FIG. 8 is a configuration block diagram showing an example of a conventional input signal conversion circuit.

FIG. 9 is a configuration block diagram showing an example of a conventional output signal conversion circuit.

[Explanation of symbols]

 T1, T2 a pair of external terminals 11 current signal receiving means 12 regulator 13 mode switching circuit 14 setting means 15 signal output means R1, R2, R resistance SR signal extraction terminal SS signal application terminal

Claims (8)

[Claims] 1. A pair of external terminals to which a transmission line is connected, a current signal receiving means for receiving a current flowing through the transmission line, a constant current mode for outputting a constant current to the external terminal, and a constant terminal for the external terminal. A regulator configured to be operable in both constant voltage modes for outputting a voltage, and mode switching means for switching the regulator to a constant voltage mode or a constant current mode according to the type of field device connected to an external terminal. And a signal input / output device equipped with. 2. When inputting a current signal to an external terminal, the mode switching means sets the regulator in a constant voltage mode, outputs a predetermined voltage to the external terminal, and extracts the current signal from the current signal receiving means. The signal input / output device according to claim 1, wherein 3. When outputting a current signal to an external terminal, the mode switching means sets the regulator in a constant current mode, gives a signal to be transmitted to the regulator, and transmits the current to be output to the external terminal. The signal input / output device according to claim 1, wherein the signal input / output device is controlled by a signal. 4. When inputting a voltage signal to an external terminal, the mode switching means applies a signal of a predetermined value to the regulator and sets the regulator to the minute current output mode or the cutoff mode, and receives from one external terminal. The signal input / output device according to claim 1, wherein a voltage signal is taken out. 5. When outputting a voltage signal to an external terminal, the mode switching means sets the regulator to a constant voltage mode, gives a signal to be transmitted to the regulator, and transmits the voltage to be output to the external terminal. The signal input / output device according to claim 1, wherein the signal input / output device is controlled by a signal. 6. The signal input / output device according to claim 1, wherein another external terminal connected to the ground is provided, and when the voltage signal is output, the one external terminal is used. 7. A resistor connected between the other of the external terminals and the ground is used as the current signal receiving means, and this resistor is shared to set the regulator in the constant current mode. The signal input / output device described. 8. The current signal receiving means is composed of a resistor connected between the other of the external terminals and the ground, and an amplifier having this resistor as a feedback resistor and having one input terminal connected to the ground. The signal input / output device according to claim 1, wherein a signal input / output device is used.