JPH0465600B2 - - Google Patents

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]

FIG. 2 shows a communication system using a conventional controller. In the figure, 1 is a transmitter with a built-in microcomputer that can change the measurement range, 2 is a portable communication device as a portable communication device, and 3 is a transmitter with a built-in microcomputer that can change the measurement range.
is a controller, E is a power supply, R is a receiving resistor, and N1 and N2 are nodes. Also, iT 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, T1 and T4 are the periods when the oscillator 1 is in analog mode;
2 and T3 are periods in which the oscillator 1 is in digital mode. Normally, an analog signal S1 for a period T1 is transmitted from the transmitter 1 to the controller 3. When it is desired to change the range of the transmitter 1 in this state, the portable communication unit 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, Portable Comunicator 2 will wake up (WAKE-UP)
Send 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 the period T4, analog signal S5 is transmitted similarly to the period T1.

[Problem to be solved by the invention]

However, in a communication system using a conventional controller, when the transmitter 1 and the portable communication unit 2 are performing digital communication for changing the range of the transmitter 1, the digital signal is transmitted to the controller 3. Since it is input as is, controller 3
A digital signal is input as a process quantity signal to the PID controller (see Figure 1), and the PID
The output signal of the controller was disturbed and had an adverse effect on the control system.

[Means to solve the problem]

In order to solve such problems, 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. When the connection of the communication device is detected, the switching means performs a switching operation so that the deviation between the process amount signal value and the process target value is made zero.

[Effect]

In the communication system according to the invention, the controller is not affected by 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 communication unit, as well as the signals on the power supply voltage and the receiving resistor, can be easily taken out by wiring around the controller.

By connecting the signal plug of the portable communication unit 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, 4 is a detection means for detecting whether or not the portable communication unit 2 is connected, 5 is a relay as a switching means that can be switched by a signal from the detection means 4, and 5a is a Contact point of relay 5, 6 is process target value setter, 7 is PID controller, 8 is target value indicator that indicates process target value, 9 is transmitter 1
E is a power supply, and R is a receiving resistor.

The controller connection port of the portable communication unit 2 shown in Fig. 1 is a simple plug connection, and the controller 3
The side is structured to accept the above plug,
The detection means 4 electrically or mechanically detects plugging. 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 PID controller 7. When the plug of the portable communication unit 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 detection 5a of the relay 5 is pushed down,
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. The transmitter 1 and the portable communication unit 2 change the range of the measured value through 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 changes the range of the measured value to the target value setter. A set value of 6 will be equal to this measured value.

When the connection between the portable communication unit 2 and the controller 3 is broken, the relay connection 5a falls upward.
Normal regulatory control takes place. In addition, in the controller 3, by disconnecting the plug of the portable communication unit 2, the process target value setting device 6 can be set.
holds the previous value as the set value, and
A sequence is set so that the adjustment mode is 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 connection of a portable communication device;
It has a switching means that can be switched by a signal from this detection means, and when the connection of a portable communication device is detected, the switching means performs a switching operation to eliminate the deviation between the plug target value and the measured value. By doing so, even if a digital signal is input to the controller during communication between the transmitter and the portable communication device, an erroneous signal will not be output from the controller. It has the effect of preventing negative effects.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a communication system according to the present invention, Fig. 2 is a circuit diagram showing a communication system using a conventional receiving instrument, and Fig. 3 is a time diagram for explaining the operation of the communication system in Fig. 2. It's a chat. 1... Transmitter, 2... Portable communication unit,
3...Controller, 4...Detection means, 5...Relay, 5a...
Relay contact, 6... Process target value setter, 7...
PID controller, 8... Target value indicator, 9... Measured value indicator, E... Power supply, R... Receiving resistance.

Claims (1)

[Claims] 1 Obtain the process quantity signal from the transmitter via the two-wire transmission line, perform control calculations based on the deviation between the process quantity signal value and the process target value, and connect the portable communication device to the two-wire transmission line. In a communication system that enables digital communication with the transmitter by connecting in parallel with the portable communication device, the communication system includes a detection means for detecting connection of the portable communication device, and is switchable by a signal from the detection means. and switching means, wherein when connection of the portable communication device is detected, the switching means performs a switching operation to make the deviation zero.