JP2002175112A - Control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constitution capable of checking signals from a field measuring instrument to see whether or not the signals are normal, without separating the measuring instrument itself from a control system. SOLUTION: The control system, which transmits a current signal corresponding to a process value from the field measuring instrument to control equipment, includes a signal relay for sending to the control equipment a false signal selectively switched from the current signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided between a field instrument (a transmitter for differential pressure, pressure, temperature, etc.) used in a plant or the like and a control device of a control system. The present invention relates to a control system that improves the maintainability of a field instrument by temporarily replacing a signal from a field instrument with a pseudo signal and transmitting the pseudo signal.

[0002]

2. Description of the Related Art In a plant or the like, as shown in FIG.
For example, a field instrument 100 that outputs a current of 0 mA, such as a differential pressure transmitter, a pressure transmitter, or a temperature transmitter, and a current signal of 4 to 20 mA from the field instrument 100 is input to perform various controls. The control device 200 is installed to configure a control system.

A field instrument 100 has a sensor section 110 for detecting process values such as differential pressure, pressure, and temperature, and a signal processing section 12 for processing a signal detected by the sensor section 110.
0 to 4 to 20 mA signal output unit 130 that generates and transmits a current output signal of 4 to 20 mA based on the processed signal.
It is composed of

A field instrument 1 having such a configuration
00 detects the process values such as the differential pressure, pressure, temperature, etc., and outputs a current of 4 to 20 mA in real time. As an output selection, 4 to 20 mA is inverted from the set range and output, or square root output is performed. In addition, when an abnormality occurs, the output of the current of 4 to 20 mA is intentionally swept to the plus side or the minus side so that the abnormal state is notified to the control device 200 on the partner side.

[0005]

However, in the prior art as described above, the field instrument 100
If there is no problem, the current input is converted into a signal in real time and output, and this does not cause any problem in a steady state, but some abnormality occurs and the abnormality is on the field instrument 100 side. If it is desired to check whether or not the field instrument 100 needs to be replaced during the operation of the plant.

In such a case, in the current output state,
For example, the H / L of the differential pressure transmitter as the field device 100
If the pressure equalization on the side is taken or its power supply is turned off, the output of the field instrument 100 becomes zero, so that there is a problem that the corresponding field instrument 100 needs to be disconnected from the entire system. Further, even if the output signal of 4 to 20 mA is intentionally swept to the plus side or the minus side when an abnormality occurs, it cannot be determined whether or not the field instrument 100 itself is abnormal. There is no problem.

Therefore, when examining a signal from the field instrument 100, it is necessary to adopt a configuration capable of examining whether the signal from the field instrument 100 is normal without disconnecting the field instrument 100 from the system. Rather, the present invention is directed to this point.

[0008]

The present invention for solving the above problems is as follows.

(1) A control system for transmitting a current signal corresponding to a process value from a field instrument to a control device, wherein a pseudo signal selectively switched to the current signal is transmitted to the control device. A control system comprising a repeater. (2) The control system according to (1), wherein the pseudo signal is output only during a time set by a timer. (3) In a control system for transmitting a current signal corresponding to a process value from a field instrument to a control device, a communication circuit for selectively switching and controlling the current signal and the pseudo signal, and outputting the current signal or the pseudo signal. And a current output conversion circuit for outputting the current signal or the pseudo signal. (4) The control system according to (3), wherein the output holding function block includes switch means for switching output of a current signal or a pseudo signal based on control from the communication circuit. (5) The output holding function block has a function of automatically canceling a pseudo signal whose output is held after a lapse of a predetermined time when switching to output the pseudo signal. 4) The control system according to the above. (6) The control according to (5), wherein the output holding function block sets a damping different from a normal setting to buffer an abrupt output fluctuation when performing the automatic release. system. (7) The control system according to any one of claims 1 to 6, wherein the signal repeater is provided between the field instrument and the control device. (8) The control system according to any one of (1) to (6), wherein the signal repeater is built in the field instrument.

As described above, in order to detect whether or not the current output signal from the field instrument is normally output,
In the signal repeater, by outputting a pseudo signal temporarily instead of the current output signal, even if some abnormality occurs and you want to check the field instrument itself, this field instrument can be output from this control system. The soundness of field instruments can be confirmed without disconnecting.

[0011]

Embodiments of a control system according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, in the control system of the present invention, a signal repeater 300 which is a characteristic part is installed between the field instrument 100 and the control device 200.

The signal repeater 300 is used for the field instrument 10.
An input monitor circuit 310 for inputting a current signal from 0;
The communication circuit 340 selectively switches and controls a current signal or a pseudo signal, an output holding function block 370 that holds a signal to be output, and a current output conversion circuit 430 that outputs a signal to the control device 200.

An input monitor circuit 310 monitors an electric current signal from the field instrument 100.
And an A / D converter 330 for converting an input signal into a digital value.

The communication circuit 340 controls a hold mode for outputting a so-called pseudo signal by selectively switching and outputting a current signal or a pseudo signal.
A communication module 350 is provided for performing control for setting a pseudo signal, for performing control for reading out a signal from an output value memory 390, control for switching a switch 380, and the like, which will be described later, and is separately controlled by a handheld terminal 360.

The output holding function block 370 includes a first switch 380 for switching between a pseudo signal and a current signal existing in an output value memory 390 for storing a pseudo signal, and a waveform in which the pseudo signal is arbitrarily set according to a user's request. , An arbitrary setting output value section 400 for outputting a signal, a timer section 410 for automatically canceling, and a second switch 420 for switching between a current signal and a pseudo signal.

As a pseudo signal, a fixed value such as the immediately preceding value or a preset value is stored in the output value memory 3.
Although it is assumed that the current value of the current signal is stored in the output value memory 390, the average value of the current signal may be calculated and stored in the output value memory 390. The output pattern up to (e.g., a fixed output pattern for each fixed period) may be stored.

Although not shown, when automatic release is performed, damping different from a normal setting is set to buffer a sudden fluctuation in output.

The current output converter 430 includes a D / A converter 440 for converting a signal from the second switch 420 into an analog value, and a constant current circuit 450 for converting the analog value into a constant current signal and outputting the signal. Is done.

The operation of the signal repeater 300 in the control system of the present invention having such a configuration will be described with reference to the flowchart of FIG.

First, it is confirmed whether or not a hold mode for generating a pseudo signal has been selected (step ST100).

When the hold mode is selected, the output hold function block 370 sets the time-up of the timer section 410 as the hold mode automatic release time (step ST110).

Next, the current input value is stored, and the hold mode is set to "ON" (steps ST120 and ST130).

Subsequently, a current signal from the field instrument 100 is input (step ST140), and if not in the hold mode, the input current signal (4 to 20 mA) is output to the control device 200 side (step ST160).

In step ST150, the hold
In the case of the mode, a current signal stored / set, that is, a pseudo signal is output (step ST170).

The pseudo signal may be outputted with a waveform arbitrarily set according to the user's request.
The average value of the current signal up to that time may be output, or the output pattern up to that time (a certain output pattern at a constant cycle or the like) may be output.

Here, the pseudo signal is transmitted until the automatic release time is released, that is, until the timer unit 410 times out, but the hold mode is released even before the automatic release time reaches. And the hold mode is set to "OFF" to output a normal current output signal of 4 to 20 mA (steps ST180, ST190, and ST190).
T200).

When the automatic release time is reached in step ST180 and the hold mode is released in step ST190, the hold mode is set to the "OFF" state and 4 to 20 mA is applied. A signal is output (steps ST180, ST190, ST200).

As described above, by providing the signal repeater 300 having the function of transmitting the pseudo signal, for example, when any abnormality occurs during the operation of the plant,
When it is desired to check whether or not the abnormality is present in the field instrument 100, the output of the signal repeater 300 is set to the hold mode, for example, the three-way valve is operated without disconnecting the field instrument 100 from the system. It is possible to confirm the soundness of the field instrument 100 only by the above.

Further, when entering this function, by arbitrarily setting the time until the hold mode is automatically released, it is possible to prevent troubles such as forgetting to release the hold mode.

In the description of FIGS. 1 and 2, the signal repeater 3
00 shows an example of a control system that is installed independently between the field instrument 100 and the control device 200, but the present invention is not limited to such an embodiment, and the entire block of the signal repeater 300 is The control system may be such that the control system 100 has a built-in control system.

[0031]

As described above, according to the control system of the present invention, when an abnormality occurs in the system, a pseudo signal similar to the current signal output from the field instrument is output instead of the field instrument. With this configuration, the operation state of the field instrument can be checked without performing an operation such as disconnection of the field instrument, and thus there is an effect that a quick operation such as maintenance can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a signal repeater according to the present invention.

FIG. 2 is a flowchart illustrating the operation of the signal repeater of the present invention.

FIG. 3 is a block diagram for explaining a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Field instrument 110 Sensor unit 120 Signal processing unit 130 4 to 20 mA signal output unit 200 Control device 300 Signal repeater 310 Input monitor circuit 320 Input monitor unit 330 A / D conversion unit 340 Communication circuit 350 Communication module 360 Handheld terminal 370 Output holding function block 380 First switch 390 Output value memory 400 Arbitrary setting output value section 410 Timer section 420 Second switch 430 Current output conversion circuit 440 D / A conversion section 450 Constant current circuit

Claims (8)

[Claims] 1. A control system for transmitting a current signal corresponding to a process value from a field instrument to a control device, wherein a pseudo signal selectively switched with the current signal is transmitted to the control device. A control system comprising a vessel. 2. The control system according to claim 1, wherein the pseudo signal is output only during a time set by a timer. 3. A control system for transmitting a current signal corresponding to a process value from a field instrument to a control device, a communication circuit for selectively switching and controlling the current signal and the pseudo signal, and the current signal or the pseudo signal. And a current output conversion circuit that outputs the current signal or the pseudo signal. 4. The control system according to claim 3, wherein said output holding function block includes switch means for switching output of a current signal or a pseudo signal based on control from said communication circuit. 5. The output holding function block has a function of automatically canceling a pseudo signal whose output is held after a lapse of a predetermined time when switching to output the pseudo signal. The control system according to claim 4, wherein 6. The output holding function block according to claim 5, wherein, when the automatic release is performed, a damping different from a normal setting is set to buffer a sudden output fluctuation. Control system. 7. The control system according to claim 1, wherein the signal repeater is provided between the field instrument and the control device. 8. The control system according to claim 1, wherein the signal repeater is built in the field instrument.