JPH01305697A - Communication system - Google Patents

Abstract

PURPOSE:To prevent an adverse effect to a control system by a communication digital signal by executing a switching operation with a switching means and making the deviation between a process desired value and a measured value into zero when the connection of a portable communicator is detected. CONSTITUTION:In an automatic mode, a contact 5a of a relay 5 is connected to an upper side, and the process desired value and a process quantity signal are inputted to a PID controller 7. When the plug of a portable communicator 2 is connected to the end connection of a controller 3 under this state, a detecting means 4 detects the connection and drives the relay 5, the contact 5a is connected to a lower side, and the digital signal as the process quantity signal is inputted to both two inputs of the PID controller 7. Thus, the process desired value and the measured value coincide with each other all the time, and in the PID controller 7, a control output in an actual state never changes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication system, and particularly to a communication system for controlling a process based on a deviation between a process measurement value and a process target value.

[Conventional technology]

A communication system using a conventional receiving instrument is shown in FIG. In the figure, ■ is a transmitter with a built-in microcomputer that can change the measurement range, 2 is a portable communicator as a portable communication device, 3 is a receiving instrument, E is a power source, and R is a portable communicator.
is the receiving resistance, and N1 and N2 are the nodes. Also, i
T is the oscillator output current, and iS is the portable communicator transmission current.

Next, the operation of this communication system will be explained using FIGS. 2 and 3. In FIG. 3, TI and T4 are periods in which the oscillator 1 is in analog mode, and T2 and T3 are periods in which oscillator 1 is in digital mode. Normally, an analog signal s1 for a period T1 is transmitted from the transmitter 1 to the receiver 3. When it is desired to change the range of the transmitter 1 in this state, the portable communicator 2 is connected in parallel with the signal line, that is, between nodes N1 and N2, and digital communication with the transmitter 1 is performed. Next, the portable comic unicake 2 emits a wake-up (WAKE-UP) pulse S2. When the transmitter 1 receives the wake-up pulse, it switches the output mode from analog transmission to digital transmission at the beginning of period T2. Next, the portable communicator 2 transmits a command signal S3, the transmitter 1 receives it, and transmits a response signal S4 shown in a period T3, which the portable communicator 2 receives. After transmitting the response signal S4, the transmitter 1 automatically returns to the analog mode in a period T4. In period T4, analog signal S5 is transmitted similarly to period TI.

[Problem to be solved by the invention]

However, in a communication system using a conventional receiving instrument, when the transmitter 1 and the portable communicator 2 are performing digital communication to change the range of the transmitter 1, the digital signal is directly transmitted to the receiving instrument 3. As a result, a digital signal was input as a process quantity signal to the PID controller (see Figure 1) of the receiving instrument 3, which disturbed the output signal of the PID controller and had a negative impact on the control system. .

[Failure to solve the problem]

In order to solve such problems, a communication system according to the present invention includes a detection means for detecting connection of a portable communication device, and a switching means that can be switched by a signal from the detection means. When the connection of the process quantity signal value and the process target value is detected, the switching means is caused to perform a switching operation to make the deviation between the process quantity signal value and the process target value zero.

[Effect]

In the communication system according to the invention, the receiving instrument is not affected by the digital signals in the digital communication between the transmitter and the portable communicator.

〔Example〕

First, an overview of the present invention will be explained. The present invention focuses on the fact that the digital signals necessary for digital communication between the transmitter and the portable communicator, as well as the signals on the power supply voltage and the receiving resistor, can be easily extracted by wiring around the control meter as the receiving instrument. It is.

By connecting the signal plug of the portable communicator to the controller, the operating mode of the controller is automatically changed. By releasing the signal plug from the controller after changing the measurement range of the transmitter, it is possible to automatically shift to the adjustment control mode after changing the measurement range without bumping. The communication system according to the present invention has such an operating circuit configured on the controller side.

FIG. 1 is a block diagram showing an embodiment of a communication system according to the present invention. In the figure, 3 is a controller as a receiving instrument, 4 is a detection means for detecting whether or not the portable communicator 2 is connected, 5 is a relay as a switching means that can be switched by a signal from the detection means 4, and 5
a is a contact of the relay 5, 6 is a process target value setter, 7 is a PID controller, 8 is a target value indicator that indicates the process target value, and 9 is a measured value indicator that indicates the process amount from the transmitter 1. , E is a power supply, and R is a receiving resistor.

The controller connection port of the portable communicator 2 shown in FIG. to be detected. The controller 3 has an automatic mode and an interlock mode, and is normally in the automatic mode.

In the automatic mode, the contact 5a of the relay 5 is connected to the upper side, and the process target value and the process amount signal are input to the PrD controller 7.

When the plug of the portable communicator 2 is connected to the connection port of the controller 3 in this state, the detection means 4 detects the connection and drives the relay 5. As a result, the contact 5a of the relay 5 is pushed down, and a digital signal as a process amount signal is input to both of the two inputs of the PID controller 7.

That is, the process target value and the measured value always match, and the current control output of the PID control unit 7 does not change. Transmitter 1 and Baukpull communicator 2
The range of the measured value is changed by digital communication, but at this time, the process target value setter 6 of the controller 3 tracks the measured value whose range has been changed, and the set value of the target value setter 6 is matched with this measured value. be equal.

When the connection between the portable communication unit 2 and the controller 3 is broken, the relay contact m 5 a falls upward, and normal adjustment control is performed. In addition, in the controller 3, by disconnecting the plug of the portable communicator 2,
A sequence is set so that the process target value setter 6 holds the immediately previous value as the set value and the adjustment mode is set to automatic mode.

By the above-described operation, the measurement control loop can change the range without any trouble to the control system.

〔Effect of the invention〕

As explained above, the communication system according to the present invention includes a detection means for detecting the connection of a portable communication device, and a switching means that can be switched by a signal from the detection means, and detects the connection of the portable communication device. By causing the switching means to perform a switching operation when this happens, the deviation between the plug target value and the measured value is zero, so that even if a digital signal is input to the receiving instrument during communication between the transmitter and the portable communication device, Since no erroneous signal is output from the receiving instrument, there is an effect of preventing the adverse influence of the communication digital signal on the control system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a communication system according to the present invention, and FIG.
The figure is a circuit diagram showing a communication system using a conventional receiving instrument, and FIG. 3 is a time chart for explaining the operation of the communication system of FIG. 2. 1... Transmitter, 2... Portable communicator,
3... Controller, 4... Detection means, 5... Relay,
5a... Relay contact, 6... Process target value setter, 7... PID controller, 8... Target value indicator, 9...
...Measurement value indicator, E...power supply, R...receiving resistance.

Claims (1)

[Claims] A process quantity signal is obtained from a transmitter via a two-wire transmission line, a control calculation is performed based on the deviation between this process quantity signal value and a process target value, and the portable communication device is connected to the
A communication system that enables digital communication with the transmitter by connecting in parallel with a wire transmission line, comprising: a detection means for detecting connection of the portable communication device; and a detection means switchable by a signal from the detection means. a communication system, the communication system comprising: switching means, wherein when connection of the portable communication device is detected, the switching means performs a switching operation to make the deviation zero.