JPS61207922A - Electropneumatic converter - Google Patents

Abstract

PURPOSE:To execute easily a correction and a maintenance by providing a correcting voltage circuit for detecting a shift of a comparing signal to a pneumatic pressure signal, and correcting its shift. CONSTITUTION:An electropneumatic converter is provided with a piezoelectric element flapper 1, a nozzle 2, a pilot relay 3, a pressure sensor 4, a signal converter 5, a comparator 7 and a correcting circuit 8. An output of the comparator 7 is varied extending from -30V to +30V, therefore, the output of the comparator 7 is set so as to become a characteristic shown by a full line, and with regard to a difference -15V to its broken line, the correcting circuit 8 generates a correcting voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an electro-pneumatic converter, for example an electro-pneumatic converter used for testing industrial instruments.

(b) Prior Art FIG. 3 shows a circuit block diagram of a commonly used electro-pneumatic converter.

In FIG. 3, electrodes 1a and 1b of the piezoelectric flapper 1
During this time, a voltage from a comparator 7 is applied, and the tip of the flapper 1 is displaced in accordance with the applied voltage.A nozzle 2 is disposed opposite to the tip of the flapper 1, and supply pressure is applied to the pilot relay 3. Supply pressure is blown out from the nozzle 2 to the tip of the flapper 1, and an output pressure corresponding to the back pressure is derived.

Further, this output pressure is converted into an electric signal by the pressure sensor 4, and the electric signal is converted by the signal converter 5 into a signal having the same level as the input signal level input to the input terminal 6, and one of the comparator 7 is added to the input end. On the other hand, the input signal applied to the input terminal 6 is also applied to the other input terminal of the comparator 7, and a voltage corresponding to the difference between the two human power signals is outputted from the comparator 7, and between the two electrodes 1a and lb of the flapper 1. It is now applied. Then, the comparator 7
The output becomes O, and the displacement of the flapper 1 becomes balanced. Therefore, the output pressure is derived according to the input signal applied to the input terminal 6.

(c) Problems to be Solved by the Invention When the above-mentioned conventional electro-pneumatic converter is used for testing industrial measuring instruments, for example, industrial measuring instrument testers often use various electrical signals and pneumatic signals for testing. However, in some cases, it outputs only electrical signals and does not use pneumatic signals. In such a case, although an electrical signal is input, the supply pressure at the electro-pneumatic converter may be cut off.

Therefore, in the conventional circuit shown in FIG. 3, an electrical signal is input to the input terminal 6, a voltage corresponding to the input signal is applied to the flapper 1 via the comparator 7, and an output pressure corresponding to the voltage is derived. However, since the output pressure does not lead out all the heat, the tip of the flapper 1 is displaced downward in an attempt to close the distance from the nozzle 2. This state of downward displacement continues for 41 times. Therefore, even if supply pressure was supplied to pilot relay 3 to output air pressure and an attempt was made to operate this electro-pneumatic converter in a normal state, the tip of flapper l did not return completely and drifted. state. Therefore, the test air pressure with an error will be output.

In view of the above, an object of the present invention is to provide an electro-pneumatic converter that can derive an output pressure without error with respect to an input signal even if the flapper 1 drifts.

(d) Means and operation for solving the problem In order to solve the above problem, the present invention first calculates the normal relationship between the input signal, the comparator output signal, and the pneumatic pressure signal, and then calculates the pneumatic pressure signal. A circuit is provided that detects a deviation in the comparison signal with respect to the reference signal and generates a correction voltage to correct the deviation.

That is, the electro-pneumatic converter of the present invention includes a flapper (1) that is displaced according to the amount of applied electricity, a nozzle (2) disposed opposite to the flapper, and a nozzle (2) that receives supply pressure and that is displaced according to the back pressure from the nozzle. a pilot relay (3) that derives the output pressure, a pressure sensor (4) that converts the output pressure into an electrical signal, and a signal converter (5) that amplifies the output of this pressure sensor to an input signal level; It consists of a comparator (7) that compares the input signal and the signal converter output, and a correction circuit (8) that receives the output of the comparator and the output of the signal converter and generates a predetermined correction voltage. , the correction voltage of the correction circuit is superimposed on the output of the comparator, and the voltage is applied to the flapper.

With this electro-pneumatic converter, even if the flapper drifts,
A voltage corresponding to the drift is generated in the correction circuit and superimposed on the output of the comparator in a corrected form, so that there is no deviation in the relationship between the input signal and the output pressure.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a circuit block diagram of an electro-pneumatic converter showing one embodiment of the present invention.

The electro-pneumatic converter of this embodiment includes a piezoelectric flapper 1, a nozzle 2, a pilot relay 3, a pressure sensor 4, and a signal converter 5.
, comparator 7, the basic configuration is the same as that of the conventional electro-pneumatic converter shown in FIG.

This correction circuit 8 is configured to further superimpose a predetermined correction voltage on the output E2 of the comparator 7 and input it to the piezoelectric element flapper 1.

FIG. 2 shows the relationship between the output voltage and output pressure of the comparator 7 of the electro-pneumatic converter of the above embodiment. In a normal case, it is as shown by the solid line, and the comparator output is set to Ov when the output is 0.6 (kg/cd). Assuming that the output of the comparator 7 varies from -30V to +30V, the input signal input to the terminal 6, the comparator output, and the air pressure have the following relationship.

The piezoelectric element flapper 1 drifts without the correction circuit 8, and the relationship between its output pressure and the output voltage of the comparator 7 is as follows.
Assuming that the characteristic drifts to the one shown by the broken line in FIG. 2, 0.
At 2 kgf/cj, the output voltage of comparator 7 is -30V
Therefore, the output voltage of the comparator 7 becomes the minimum value, and if it drifts further to the negative side, the normal input/output characteristics of the electro-pneumatic converter will no longer be maintained.

In this case, it is only necessary to return the characteristic shown by the broken line in FIG. 2 to the characteristic shown by the solid line, so the output of the comparator 7
The characteristic shown by the solid line in the figure is obtained, and the difference of -15V from the broken line can be superimposed by the correction circuit 8. Therefore, the correction circuit 8 is configured to generate this correction voltage. That is, the correction circuit 8
When the output voltage of the comparator 7 is EI and the output voltage of the comparator 7 is Et, as a result of the calculation, eo becomes O
It is considered normal when , and if it becomes larger than a certain value, the drift is large, so a correction voltage is generated.

For example, when EI=5VSEx-OVO, e0='l■, so in this case, the correction circuit 8 generates -15V. Therefore, in order for Ov to be input to the piezoelectric element flapper 1, the output of the comparator 7 becomes +15V, returning to the normal operating range.

In this case, one 15V of the correction circuit 8 will be fixed for the time being. This is because once corrected, the drift itself is very gradual and there is no need to frequently correct it.

(F) Effects of the Invention According to this invention, the output of the signal converter and the output of the comparator are compared, and if they are not in a constant relationship, a correction circuit is used to adjust the voltage accordingly so that the output is in a normal state. is generated and the correction voltage can be corrected thereafter, so even if the flapper drifts, it is very easy to correct it.

Furthermore, v4Iv! Maintenance is also extremely easy, since it is only necessary to adjust the correction voltage again when drift occurs again after a period of time has passed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electro-pneumatic converter showing an embodiment of the present invention, and FIG. 2 is a diagram illustrating the relationship between output pressure and comparator output to explain the operation of the electro-pneumatic converter. , FIG. 3 is a block diagram showing a conventional electro-pneumatic converter. 1: Piezoelectric flapper, 2: Nozzle, 3: Pilot relay, 4: Pressure sensor, 5: Signal converter,
7: Comparator, 8: Correction circuit. Patent applicant: Shimadzu Corporation Agent
Patent Attorney Shigeru Nakamura %1 Figure

Claims (1)

[Claims] (1) A flapper that is displaced according to the amount of applied electricity, a nozzle installed opposite to the flapper, a pilot relay that receives supply pressure and derives an output pressure according to the back pressure from the nozzle, and It has a pressure sensor that converts it into an electrical signal, a signal converter that amplifies the output of this pressure sensor to an input signal level, and a comparator that compares the input signal and the output of the signal converter, and the output of the comparator The electro-pneumatic converter in which a corresponding voltage is applied to the flapper includes a correction circuit that receives the output of the comparator and the output of the signal converter and generates a predetermined correction voltage; An electro-pneumatic converter characterized in that the voltage is applied to a flapper.