JPS624721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process control system that transmits an output signal from a controller as an optical signal.

In conventional systems, when controlling a control valve installed on site, there are two methods: sending an air signal from the controller to control the air valve, and sending an electrical signal from the controller via an electro-pneumatic converter installed in the middle. There are methods for controlling air valves. The former method is
Although it is suitable for intrinsically safe explosion-proof instrumentation, it is not suitable for large-scale instrumentation because there is a delay in signal transmission and the instrumentation uses air piping, making it difficult to connect to a computer. The latter method is not suitable for intrinsic safety because it transmits electrical energy, requires various safety barriers, and
Mixing noise becomes a problem.

The present invention solves these various problems in conventional devices, and one of the features of the present invention is that the controller outputs an optical signal, and the actuator receives an optical signal transmitted through an optical fiber. There is.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a process controller, and its output signal is transmitted through two efficient light emitting diodes 11,
12, for example, as shown in FIG. 2, two types of pulse width signals PW1 and PW2 are outputted, and the pulse widths of these pulse width signals serve as signals for controlling the operating end. The light emitting diode 11 emits, for example, red light in response to the pulse width signal PW1, and the light emitting diode 12 emits, for example, green light in response to the pulse width signal PW2. Reference numeral 2 denotes an optical fiber transmission line whose both ends are branched into two parts, one of which is divided into two halves, where a light emitting diode 11 and a light emitting diode 12 are coupled, respectively, and two types of light from there are transmitted to the other end. Ru. 3 is an actuator installed at the site, which receives the optical signal transmitted via the optical fiber transmission line 2 via filters 31 and 32;
It has two light receiving diodes 41 and 42. These two light receiving diodes 41 and 42 are connected in parallel with opposite polarities, and the output signal e _r of this parallel diode circuit is applied to the force motor 51, which moves the flapper 52 in the directions of arrows a and b about the fulcrum 53. Displace it to. Reference numeral 54 designates a nozzle that together with the flapper 52 constitutes a nozzle/flapper mechanism.The nozzle 54 has an injection port facing the flapper 52, and generates back pressure corresponding to the displacement of the flapper 52. The pilot relay 55 amplifies the nozzle back pressure and supplies the amplified air pressure Po to the feedback bellows 56 and outputs it to the air valve 6. The force generated by the feedback bellows 56 is generated by the force motor 5.
1 is in the opposite direction to the force generated, and the force is balanced so that the moments of both are equal, and the output pressure Po to the air valve 6 in this balanced state corresponds to the output e _r from the parallel diode circuit, The air valve 6 is operated by the output pressure Po.

In the device configured in this way, the output signal from the controller 1 is the difference in pulse width between two types of pulse width signals PW1 and PW2, and these two types of pulse width signals are transmitted through the optical fiber transmission line 2. The optical signal is transmitted to the actuator 3 installed at the site. Therefore, there is no delay in signal transmission, and there is no need for special means for intrinsically safe explosion-proofing, noise countermeasures, signal isolation, etc., and instrumentation can be performed at low cost.

In the actuator 3, the red optical signal transmitted from the controller 1 is selected by the filter 31,
The light is received by the light receiving diode 41 , and the green light signal is selected by the filter 32 and received by the light receiving diode 42 . Each light receiving diode 41, 42
, a current corresponding to the pulse width of the received light flows therein, and the output signal e _r of the parallel diode circuit, that is, the current flowing to the force motor 51 corresponds to the difference in pulse width between the pulse width signals PW1 and PW2. A current flows.

In this way, the output signal from the controller 1 side is
The difference between the different pulse width signals is output, and this is transmitted as an optical signal of two types of red and green pulse width signals through one optical fiber transmission line, and the actuator 3 outputs the two types of pulse width signals. When the force motor 51 is operated with the difference in the light emitting diode 1
It has the advantage of not being affected by changes in the characteristics of the 1, 12 optical fiber transmission line 2 and the light receiving diodes 41, 42.

FIG. 3 is a block diagram showing the main parts of another embodiment of the present invention. In this embodiment, two optical fiber transmission lines are used.
Two types of pulse width signals PW1 and PW2 from the light emitting diodes 11 and 12 are transmitted as optical signals to the actuator 3 side via the respective transmission lines 21 and 22. It was designed to do so. Although two transmission lines are required, there is an advantage that there is no need to transmit two types of pulse width signals as a red signal and a green signal, and there is no need for a filter means for selecting these as in the embodiment of FIG. There is.

In this embodiment, the output signal of the controller 1 may be outputted to the light emitting diodes 11 and 12 as a difference in light intensity. In this case, the two types of light intensity signals transmitted through the two transmission lines 21 and 22 are converted into a current signal corresponding to the difference in light intensity between the two in a parallel circuit of light receiving diodes 41 and 42, which drives the force motor. .

In each of the above embodiments, the optical signal output from the controller 1 may be a laser beam.
Further, in the actuator 3, the conversion from an electric signal to a pneumatic signal may be performed by a configuration other than a force motor, a nozzle flapper, a pilot relay, or a feedback bellows.

As explained above, in the device according to the present invention, no electrical signal is involved in transmitting the signal from the controller to the operating end of the air valve or the like. Therefore, there is no need for special considerations such as intrinsically safe explosion-proof measures, noise measures, or signal isolation.
Furthermore, an inexpensive device with overall instrumentation without delay in signal transmission can be realized.

Further, in the device according to the present invention, the process controller outputs two types of optical signals whose pulse width or light intensity differentially changes depending on the output signal, and the actuator has two types of optical signals. For example, although the light receiving diode circuit is transmitting the optical signal, the pulse width of the two types of optical signals is different. When both (or light intensities) are equal, it is set as 0, and an electric signal convenient for controlling the operating end can be obtained with a simple configuration via an electro-pneumatic converter that changes polarity between positive and negative.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a waveform diagram showing the form of the output signal of the controller in the embodiment shown in FIG. 1, and FIG. 3 is a configuration diagram showing the main part of another embodiment of the present invention. 1... Process controller, 11, 12... Light emitting diode, 2... Optical fiber transmission line, 3... Actuator, 41, 42... Light receiving diode, 5
1...Force motor, 6...Air valve.

Claims (1)

[Claims] 1. A process controller that outputs two types of optical signals whose pulse width or optical intensity differentially changes depending on the output signal, and an optical fiber transmission that transmits the optical signals from this controller. A light receiving diode circuit is connected in parallel with opposite polarity to each receive two types of optical signals transmitted through this optical fiber transmission line, and an electric signal from this light receiving diode circuit is converted into a pneumatic signal and sent to the operating end. A process control system comprising an actuator having an electro-pneumatic conversion means for supplying. 2. The process control system according to claim 1, wherein the optical signals output from the process controller are two types of optical signals with different wavelengths, and the optical fiber transmission line is configured with one optical fiber. .