JP3266919B2 - Pulse air pressure transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse air pressure converter which receives an electric pulse signal from a control system to generate an air pressure necessary for a pneumatic valve used in a process control and converts the signal into an air pressure.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional pulse pneumatic converter includes an UP (increase) signal transmitted from a control system,
Pulse motor drive circuit 71 receiving DOWN (decrease) signal
A pulse motor 72 driven by the pulse motor drive circuit 71; a pneumatic input / output mechanism 73 that displaces the flapper and outputs air pressure corresponding to the displacement of the flapper as the pulse motor 72 advances; A potentiometer 74 for detecting the advance position, and converting the resistance of the potentiometer 74 into an electric current.
An R / 1 converter 75 for feeding back a current of ２０20 mA to the control system and a power supply circuit 76 receiving a power supply voltage from the control system are provided.

[0003]

Generally, a pulse air pressure transducer is provided on the site (field) and is often more than 100 m away from a room where a control system is installed. However, in the above-described conventional pulse air pressure converter, when connecting to the instrumentation panel of the control system, three of UP, DOWN, and CON (common) are used for increasing and decreasing the electric pulse.
2 for answerback signal, 2 for power supply
If the pulse air converter is far from the control system, there is a problem that the instrumentation cost increases.

[0004] The present invention has been made in view of the above problems, and provides a pulse-pneumatic converter capable of keeping the instrumentation cost low even in a place far from the control system. It is an object.

[0005]

A pulse air pressure converter according to the present invention receives a pulse signal for increasing or decreasing an output air pressure, outputs an output air pressure corresponding thereto, and outputs an analog signal corresponding to the output air pressure. the in what feedback to instrumentation panel side as answer back signal, a connection line between the instrumentation panel, the DC power supply, the common line, and a three answer back signal, among these three connection lines, the common An increase / decrease signal from the instrumentation panel is superimposed and received using a line and an answerback signal line .

[0006] In the pulse pressure transducer, a connecting line and the common line for power supply, is supplied direct-current power supply voltage, answer-back signal in the connection line and the common line for answer back is transmitted, the A Nsabakku signal to further A pulse signal for increasing or decreasing is transmitted by being superimposed on the answerback signal of the connection line and the common line.

[0007]

The present invention will be described in more detail with reference to the following examples. FIG. 1 is a circuit diagram showing one embodiment of the present invention. In the figure, a DC power supply 2 of a control system 1;
The feedback resistor 3 is connected in series. Control system 1 and pulse air pressure converter 12 in field 11
It includes a connection line L ₁ for power supply, a common line L _2, are connected by three connection lines of the connecting line L ₃ for answer back.
The control system 1, the pulse generator 4 which outputs a pulse for increasing or decreasing is provided, the output of the pulse generator 4 is connected to the connection line L ₃ of the common line L ₂ and the answer-back signal . As shown in FIG. 3 , the pulse generator 4 outputs a positive pulse signal in the case of an increase, and outputs a negative pulse signal in the case of a decrease. As shown in FIG. 2, the pulse air pressure converter 12 includes a pulse receiver 13, which determines the polarity of the pulse signal input by the pulse receiver 13, and determines an UP signal or Outputs a DOWN signal.

[0008] In this example, when outputting a pulse signal for increasing or decreasing the pulse generator 4, the current i ₁ shown in Figure 1 to the common line L _2, i ₂ flows, but the resistance value of the resistor 3 Normally, the input resistance is 250Ω, but the input resistance of the pulse receiver 13 is designed to be extremely smaller than 250Ω. As a result, i ₁ ≪i ₂ and i ₁
Does not affect the original answerback signal of 4 to 20 mA.

The polarity of the current i ₂ is determined by the pulse receiver 13. If the polarity is positive, the pulse is supplied as an UP signal to a pulse motor drive circuit (not shown). , And the pulse is supplied to the pulse motor drive circuit as a DOWN signal. The pulse air pressure converter 12
Is converted to an electric signal and fed back to the control system 1 as an answerback signal.

[0010]

【The invention's effect】 According to the present invention, the connection with the control system is provided.
Connect three for DC power supply, common line and answer back signal line
The increase / decrease signal is connected to the common line among these connection lines.
It is superimposed on the answerback signal line and transmitted.
Thus, the number of connection lines can be reduced, and the instrumentation cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a pulse receiver employed in the embodiment.

FIG. 3 shows an UP signal, DOWN used in the embodiment of FIG . 1;
FIG. 4 is a waveform chart showing signals.

FIG. 4 is a block diagram showing a conventional pulse air pressure converter.
is there.

[Explanation of symbols]

L ₁ power connection line L ₂ common connection line L ₃ answer-back connecting wire 4 pulse generators 13, 13a, 13b pulse receiver

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F15B 5/00 G08C 19/18

Claims (1)

(57) [Claims] 1. A method for receiving a pulse signal for increasing or decreasing an output air pressure, outputting an output air pressure corresponding to the pulse signal,
In a pulse air pressure converter that feeds back an analog signal corresponding to the output air pressure as an answerback signal to an instrumentation panel side, a connection line with the instrumentation panel is a DC power supply, a common line, and an answerback signal. , of these three connection lines
A pulse air pressure converter, wherein a common line and an answer back signal line are used to receive an increase / decrease signal from the instrument panel in a superimposed manner.