JPH06129402A - Electric-pneumatic converter - Google Patents

Abstract

PURPOSE:To realize quick abnormality discrimination by operating a variation between return voltage and input voltage responding to an electric current signal received from a controller, seeking an air pressure signal from the variation and converting it into a signal to respond to the previous return voltage, and at the same time conducting abnormality indication at the time of the variation being outside a regular range. CONSTITUTION:An electric current signal responding to an air pressure signal P0 to be set is inputted from a controller through transmission lines L1, L2, and a variation amplifier 12 operates a variation between input voltage Vi and return voltage Vf, and variation voltage VD is outputted. A drive circuit 14 drives a displacement/air pressure converter 13 by means of the variation voltage VD, and the air pressure signal P0 responding to the variation voltage VD is made to be operated. This air pressure signal P0 is converted into the return voltage Vf through a pressure/electricity converting portion 15 and a zero/span setting circuit 16. Meanwhile, the existence of abnormality in the variation voltage VD is discriminated by means of a variation discriminating circuit 20, and abnormality indication is made at an LCD 23 by outputting an abnormality signal Va at the time of abnormality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electropneumatic converter which receives a current signal from a control device through two transmission lines and outputs a pneumatic signal corresponding to the current signal, and in particular, an abnormality occurs. The present invention relates to an electro-pneumatic converter improved so that this abnormality can be immediately recognized on the LCD when it is damaged.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing the structure of a conventional electropneumatic converter. In the figure, a pneumatic signal P to be set from a control device or the like via two transmission lines L ₁ and L _2.
The current signal I ₀ corresponding to ₀ is input to the input terminal T of the electropneumatic converter 10.
₁ transmitted to T ₂ .

A power supply circuit 11 composed of a Zener diode and an input resistance R _i are connected in series to the input terminals T ₁ and T ₂ . The connection point between the power supply circuit 11 and the input resistance R _i is connected to the common potential point COM.

An input voltage V _i proportional to the current signal I ₀ is generated at the connection point between the input resistor R _i and the input terminal T ₂ . This input voltage V _i is input to one end of the input of the deviation amplifier 12,
The feedback voltage V _f is input to the other end.

The deviation amplifier 12 calculates the deviation between the input voltage V _i and the feedback voltage V _f and outputs the deviation voltage V _D to its output end. The deviation voltage V _D is output to the drive circuit 14 which drives the displacement / pneumatic pressure converter 13, and is converted into the displacement DS corresponding to the deviation voltage V _D here. The displacement / pneumatic pressure converter 13 is composed of, for example, a nozzle / flapper mechanism and a pilot relay, and the drive circuit 14 is composed of, for example, an electromagnetic actuator.

The displacement / pneumatic pressure converter 13 has a supply air pressure SUP.
Is supplied to the displacement / pneumatic pressure converter 13 and the drive circuit 1
The signal is converted into an air pressure signal P ₀ corresponding to the displacement DS output from 4 and output to the output terminal T ₃ . Pressure / electric converter 1
5 converts this air pressure signal P ₀ into a pressure signal V _P proportional thereto.

The zero / span setting circuit 16 adjusts the zero point or span of the pressure signal V _P to a predetermined value and outputs it as a feedback signal V _{f to} the other end of the input of the deviation amplifier 12.

The air pressure signal P ₀ corresponding to the current signal I ₀ (= 4 to 20 mA) is output to the output terminal T ₃ and is output and displayed on the pressure gauge 17. As the pressure gauge 17, for example, a range of 0 to ² Kgf / cm ² is used, and a pressure range of 0.2 to 1 Kgf / cm ² is used. The scale of this pressure is, for example, 0.1 Kgf / cm ² unit, and the reading accuracy is about 0.5% to 1%.

In the configuration as described above, the current signal I ₀
Is input to the electropneumatic converter 10 via the input terminal T ₁ , this current signal I ₀ is supplied to the power supply circuit 11 and the deviation amplifier 1.
2, the driving circuit 14, the pressure / electric converter 15, and the zero / span setting circuit 16 to flow to gather at the common potential point COM, flow from the common potential point COM to the input resistance R _i, and flow out from the input terminal T ₂ . . The power supply circuit 11 uses this current signal I ₀ to generate a constant voltage V _b for supplying power to the internal circuit of the electropneumatic converter 10 and supply it to each unit.

Further, a common potential point C is provided across the input resistance R _i.
The input voltage V _i generated for the OM is applied to the deviation amplifier 12
Is applied to one end of the input terminal of. The deviation amplifier 12 calculates the deviation between the feedback signal V _f applied to the other end and the input voltage V _i, and supplies it to the drive circuit 14 as the deviation voltage V _D.

The drive circuit 14 converts the displacement voltage V _D into a displacement DS corresponding to the deviation voltage V _D and supplies the displacement DS to the displacement / pneumatic pressure converter 13. The displacement / pneumatic pressure converter 13 converts the pneumatic pressure signal P ₀ proportional to the displacement DS to output to the output terminal T ₃ and displays the output on the pressure gauge 17. Furthermore, the air pressure signal P
₀ is pressure / electric converter 15 and zero / span setting circuit 16
Is fed back to the other end of the input of the deviation amplifier 12 as a feedback signal V _f .

[0012] Thus, since the deviation amplifier 12 controls its output such that the feedback signal V _f which is proportional to the input voltage V _i and the pneumatic signal P ₀ which is proportional to the current signal I ₀ matches, as a result pneumatic signal P ₀ corresponding to the current signal I ₀
Is obtained.

[0013]

However, in the electro-pneumatic converter as described above, the output pressure cannot be accurately read in the field, and the air pressure output as a function of the current signal I _{0 as} an input is not detected. When the signal P ₀ does not follow accurately due to the abnormal operation of the electropneumatic converter, it is difficult to find the abnormality even when looking at the output display on site.

Further, it is difficult to instantly detect this abnormality when the input / output deviation is small by several percent. Therefore, there is a problem that the detection of abnormality is delayed and the accident is expanded accordingly.

[0015]

The present invention has a structure for solving the above problems, in which a current signal is received from a control device via two transmission lines, and an input voltage and feedback corresponding to the current signal are received. Deviation calculating means for calculating the deviation from the voltage and outputting the deviation signal, air pressure converting means for converting the deviation signal into a corresponding air pressure signal, and the previous air pressure signal into a signal corresponding to the previous feedback voltage. The pressure / electricity converting means for converting, the deviation determining means for monitoring whether or not the deviation signal is within the specified range and outputting an abnormal signal when the deviation signal is out of the specified range, and the abnormal signal are inputted. A display signal generating means for generating an abnormal display signal for abnormal display in a predetermined form, and an LCD drive unit for causing the LCD to display the previous abnormal display based on the previous abnormal display signal are provided.

[0016]

[Operation] The deviation calculating means receives a current signal from the control device through the two transmission lines, calculates the deviation between the input voltage and the feedback voltage corresponding to the current signal, and outputs the deviation signal.
The air pressure converting means converts the deviation signal into a corresponding air pressure signal.

The pressure / electricity conversion means converts the pneumatic signal into a signal corresponding to the feedback voltage. The deviation discriminating means monitors whether or not the preceding deviation signal is within the specified range and outputs an abnormal signal when the deviation signal is outside the specified range.

The display signal generating means generates an abnormal display signal for abnormal display in a predetermined form when the abnormal signal is input. The LCD drive unit causes the LCD to display the previous abnormality display based on the previous abnormality display signal.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. The parts having the same functions as those of the conventional electropneumatic converter shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be appropriately omitted.

Power supply circuit 11, deviation amplifier 12, drive circuit 14, displacement / pneumatic pressure converter 13, pressure / electricity converter 1
5 and the configuration of the zero / span setting circuit 16 and the like are the same as those of the conventional electropneumatic converter shown in FIG.

In addition to these components, the embodiment shown in FIG. 1 has a deviation discriminating circuit 20, a display signal generating circuit 21, and L.
CD drive circuit 22 and LCD (liquid crystal display element) 23
Has been added.

The deviation discriminating circuit 20 receives the deviation voltage V _{D and} judges whether or not this value is within a prescribed range. The deviation determining circuit 20 determines that the output air pressure signal P ₀ follows the input current signal I ₀ when the deviation voltage V _D is within the specified range, and follows the output when the deviation voltage V _D is outside the range. Since there is no abnormality, it is determined that an abnormality has occurred and the abnormality signal V _a
Is output.

The display signal generating circuit 21 is normally supplied with a pressure signal V _P proportional to the air pressure signal P ₀ from the pressure / electrical converter 15, and the pressure value (digital value) corresponding to this is inputted.
Is displayed on the LCD via the LCD drive circuit 22.

However, the error signal V is output from the deviation discriminating circuit 20.
_{When a} is input, the display signal generation circuit 21 controls the LCD display via the LCD drive circuit 22 by performing control such as blinking the pressure value displayed on the LCD.

Next, regarding these additional circuit parts,
This will be described in detail with reference to the specific circuit shown in FIG. 2 and the characteristic diagram shown in FIG. The deviation amplifier 12 includes an inverting amplification circuit and a deviation amplification circuit. The inverting amplifier circuit is composed of resistors R ₁ and R ₂ , an operational amplifier Q _{1 and the} like, and level-converts the input voltage V _i with an amplification degree determined by the ratio of the resistors R ₁ and R ₂ and outputs it to its output terminal. Output as voltage V ₀ . This output is input to the deviation amplification circuit at the next stage.

The deviation amplifier circuit includes an operational amplifier Q ₂ and a resistor R ₃
It consists of to R _6, and calculates the deviation between the output voltage V ₀ and the feedback signal V _f output to the deviation determining circuit 20 as a difference voltage V _D at its output.

The deviation discriminating circuit 20 includes resistors R ₇ , R ₈ ,
It is composed of R ₉ , R ₁₀ , comparators Q ₃ , Q _4, etc. The constant voltage V _b is divided by the resistors R ₇ , R ₈ and R ₉ , and the resistor R
The first divided voltage from the connection point of ₇ and R ₈ is the comparator Q ₃
The non-inverting input terminal (+), a second divided voltage from a connection point of the resistors R ₈ and R ₉ are the inverting input terminal of the comparator Q ₄ - are respectively applied to the ().

Furthermore, the inverting input terminal of the comparator Q ₃ (-) and the non-inverting input terminal of the comparator Q ₄ (+) difference voltage V _D is applied to, the further comparator Q _3, Q ₄ of the output open-collector And the resistor R ₁₀ functions as a pull-up resistor. As a result, they function as a window comparator as a whole, and when they deviate from the window, an abnormal signal V _a is obtained at the output terminals of the comparators Q ₃ and Q ₄ .

As shown in FIG. 3, the specified range of the window comparator is determined by the resistors R ₇ , R ₈ and R ₉ , but V _{D1 is} the reference value of the deviation voltage V _D , and the upper limit value is V _D2 ,
When the lower limit value is V _D3 , it is normal if the deviation voltage V _D exists in the range of V _D3 <V _D <V _D2 , and an abnormal signal V _a is output when it is outside this range. The output level in normal condition is V
_Oh, the output level when abnormal is V _OL . The upper limit value V _D2 and the lower limit value V _D3 are determined in consideration of the tracking accuracy.

The display signal generation circuit 21 is a level conversion circuit L.
It is composed of a CV and a microprocessor μP. The level conversion circuit LCV has an output level V of the deviation determination circuit 20.
_{Oh and} V _OL are input and level conversion is performed for output to the microprocessor μP.

On the other hand, the pressure signal V _P is converted into a digital signal by the A / D converter ADC and input to the microprocessor μP. Then, the level conversion circuit LCV
From the normal level to "H" is the microprocessor μ
When being output to P, the microprocessor μP outputs the pressure signal V _P , that is, the value corresponding to the air pressure signal P ₀ , to LC.
It is digitally displayed on the LCD via the D drive circuit 22.

However, when an abnormal level "L" is output from the level conversion circuit LCV to the microprocessor μP, the microprocessor μP corresponds to the abnormal pressure signal V _P , that is, the air pressure signal P ₀ . LC control signal for blinking values or displaying all segments
The data is output to the D drive circuit 22 to display the LCD.

FIG. 4 shows a configuration when the function shown in FIG. 1 is realized by an all digital system. Input voltage V _i
Is converted in level by the operational amplifier Q ₁ and output to the multiplexer 24. On the other hand, the pneumatic signal P ₀ is converted into a pressure signal V _P by the pressure / electric converter 15 and output to the multiplexer 24.

The multiplexer 24 is switched by the control signal from the microprocessor μP to change the input voltage V _i.
And the pressure signal V _P are read, converted into a digital signal by the A / D converter ADC, read into the microprocessor μP, and stored in the built-in RAM.

R incorporated in the microprocessor μP
A necessary calculation program is stored in the OM, and the calculation is executed according to this calculation procedure. The execution result is output as an air pressure signal P ₀ to the output terminal T ₃ via the drive circuit 14 and the displacement / pneumatic pressure converter 13, and the pressure value corresponding to the air pressure signal P ₀ is L via the LCD drive circuit 22.
Digitally displayed on CD.

The ROM calculates the deviation in the deviation amplifier 12,
Calculation in the zero / span setting circuit 16, deviation determination circuit 20
The calculation procedure corresponding to the calculation in (1) and the calculation control in the display signal generation circuit 21 is stored.

FIG. 5 shows the deviation calculation and deviation discrimination circuit 2 in the deviation amplifier 12 which is a characteristic part of the present invention.
Calculation procedures such as calculation at 0 and calculation control at the display signal generation circuit 21 are described.

In the figure, in step 1, a value corresponding to the input voltage V _i from the operational amplifier Q ₁ is read as input data through the multiplexer 24 and stored in a predetermined area of the RAM. Next, the process proceeds to step 2, and the value corresponding to the air pressure signal P ₀ which is output data is the multiplexer 24.
And is stored in a predetermined area of the RAM.

Further, proceeding to step 3, the microprocessor μP uses these data stored in the RAM to calculate the deviation of these values according to the calculation procedure stored in the ROM, and the predetermined area of the RAM is calculated. To store.

At step 4, the microprocessor μP judges whether or not this deviation is within a predetermined range (accuracy) according to a judgment procedure stored in the ROM, and if it is within the accuracy, it proceeds to step 5. Then, the value corresponding to the air pressure signal P ₀ is output to the LCD drive circuit 22. After this,
In step 6, the LCD drive circuit 22 displays the corresponding value on the LCD.
Digitally displayed on.

On the other hand, when it is determined that the abnormality is not within the predetermined range in step 4, the process proceeds to step 7 and the LCD
The control data for blinking is output to the LCD drive circuit 22. Thereafter, in step 8, the LCD drive circuit 22 blinks the corresponding abnormal value and digitally displays it on the LCD.

[0042]

As described above in detail with reference to the embodiments, according to the present invention, the output display of the LCD blinks when the input and output of the electropneumatic converter do not match in accuracy in an abnormal state. Since it is configured to display or display all segments, the abnormality of the electro-pneumatic converter can be instantly judged at the use site, and the abnormality can be detected early.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of a characteristic part shown in FIG.

FIG. 3 is a characteristic diagram illustrating the operation of the circuit shown in FIG.

FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention.

FIG. 5 is a flowchart illustrating the operation of the embodiment shown in FIG.

FIG. 6 is a block diagram showing a configuration of a conventional electropneumatic converter.

[Explanation of symbols]

 10 Electropneumatic Converter 11 Power Supply Circuit 12 Deviation Amplifier 13 Displacement / Pneumatic Converter 14 Drive Circuit 15 Pressure / Electric Converter 20 Deviation Discrimination Circuit 21 Display Signal Generation Circuit 22 LCD Drive Circuit 23 LCD

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryusaku Kubota 2-932 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Electric Co., Ltd. (72) Inventor Hiroshi Hayashi 2-932 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Minoru Midagawa 2-932 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. (72) Yasuo Kasahara 2-3-9 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Machinery Co., Ltd. (72) Inventor Akira Inoue 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Yu Iwamoto 2-39 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. In the company

Claims (1)

[Claims] 1. A deviation calculating means for receiving a current signal from a control device through two transmission lines, calculating a deviation between an input voltage and a feedback voltage corresponding to the current signal, and outputting the deviation signal. Pneumatic pressure conversion means for converting the deviation signal into a corresponding pneumatic pressure signal, pressure / electric conversion means for converting the pneumatic pressure signal into a signal corresponding to the feedback voltage, and whether or not the deviation signal is within a specified range. A deviation discriminating means for outputting an abnormal signal when the abnormal signal is outside the specified range, a display signal generating means for generating an abnormal display signal for abnormally displaying in a predetermined form when the abnormal signal is input, L that causes the LCD to display the abnormality based on the display signal
An electropneumatic converter comprising a CD drive unit.