CN208188639U - Valve feed circuit - Google Patents

Abstract

The utility model relates to valve feed circuit, which includes: bias voltage Vbias output module, 0V~+V bias voltage Vbias is exported, wherein+V is identical as ADC reference voltage；Amplifier module obtains Vadc for K times by Vfb-Vbias amplification, and wherein Vfb is the feedback voltage of valve feedback potentiometer；ADC module, for Vadc to be carried out Analog-digital Converter；MCU control circuit, for selecting the output voltage amplitude of bias voltage Vbias output module and the value of amplification coefficient K.This programme can improve the resolution ratio under small stroke of valve feedback device in the case where not dramatically increasing valve feed circuit cost.

Description

Valve feed circuit

Technical field

The utility model relates to automation fields, and in particular to a kind of valve feed circuit.

Background technique

Valve feedback device drives potentiometer rotation by valve rod, and potentiometer exports unused voltage value, and to represent valve different Position.The feedback device of existing valve positioner is fixed form, and in small stroke, resolution ratio is low.In order to reach enough resolutions Rate needs high-resolution analog-digital converter (ADC), and which increase costs.Feedback rod revolves when valve positioner is angle stroke The maximum value of gyration is generally 90 °, in Direct Travel, to guarantee the linearity, and the rotation of valve positioner feedback rod when Direct Travel Gyration maximum is generally less than 40 °.In order to adapt to the needs of different trips, for straight stroke valve, valve positioner needs to pacify The valve feedback rod of different length is filled, but due to the limitation of installation site, is adapted to the linear motion valve of small stroke in valve positioner Men Shi, the feedback angle of valve positioner position is still less than 10 °.Assuming that the resolution ratio of valve positioner 0.1%, the ADC needed Resolution requirements calculate as follows: assuming that feedback transducer uses common conductive plastic potentiometer, maximum effectively rotation angle It is 340 °, is 0.1%*90/340=0.0265% for the ADC resolution ratio that angle travel feedback angle is 90 ° of needs, uses significance bit Number is that the ADC of 12bit can satisfy requirement.It is 10 ° for Direct Travel feedback angle, the resolution ratio needed can equally calculate such as Under: 0.1%*10/340=0.00294%, it is that the ADC of 16bit is just able to satisfy device 0.1% that such case, which at least needs number of significant digit, Resolution requirement.When valve positioner uses on small straight stroke valve, in order to realize the precision of valve feedback, need Using the ADC of higher resolution, which greatly enhances the costs of valve position feedback device.Or make in different feedback angles Amplify the angle of feedback with different gear sets, so that using same group of ADC in the case where different trips or feedback angle.

Utility model content

The purpose of the utility model is to overcome the deficiencies in the prior art, provide a kind of valve feed circuit, can not show It writes in the case where increasing valve feed circuit cost, improves the resolution ratio under small stroke of valve feedback device.

The purpose of this utility model is achieved through the following technical solutions:

A kind of valve feed circuit, the circuit include:

Bias voltage Vbias output module exports 0V~+V bias voltage Vbias, wherein+V and ADC reference voltage phase Together；

Amplifier module obtains Vadc for K times by Vfb-Vbias amplification, and wherein Vfb is the anti-of valve feedback potentiometer Feedthrough voltage；

ADC module, for Vadc to be carried out Analog-digital Converter；

MCU control circuit, for selecting the output voltage amplitude and amplification coefficient K of bias voltage Vbias output module Value.

As a preferred solution of the present invention, the bias voltage Vbias output module constitutes bleeder circuit by multiple resistance, The MCU selects the output voltage of bleeder circuit by single-ended multichannel variable connector.

As a further improvement of the present invention, the amplifier module is made of subtracter multiple resistance and amplifier and can compile Journey amplifier, the MCU control amplification coefficient K by difference multi-channel digital analog switch.

As a further improvement of the present invention, the bias voltage Vbias output module is by resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, resistance R8, resistance R9 constitute bleeder circuit and export as bias voltage Vbias Circuit, totally 8 output voltages are as bias voltage Vbias for exporting VREF1 ~ VREF8 for the bleeder circuit, and output voltage is by low It is gradually increased to height, MCU controls single-ended 8 channel variable connector 4051D selection by REF1_CPU, REF2_CPU, REF3_CPU One of them in VREF1 ~ VREF8, i.e. MCU selectively export bias voltage Vbias by single-ended 8 channel variable connector 4052D, Realize programmable Vbias；

The amplifier module is by resistance R10, resistance R11, resistance R12, resistance R13, resistance R14, resistance R15, resistance R18, resistance R19, resistance R20, resistance R21, resistance R22, resistance R23 and amplifier constitute subtracter and programmable amplifier, MCU It controls two-way 4:1 multidiameter option switch by OP1_CPU, OP2_CPU and controls programmable amplifier, realize programmable times magnification Number K.

As the preferred embodiment of this programme, the bias voltage Vbias output module controls DAC by spi bus by MCU Export the Vbias of different voltages value.

As a further improvement of the present invention, the amplifier module is configured to difference amplifier by GA, by Vfb and Vadc output is generated after the difference amplification of Vbias and gives ADC, and amplification factor is configured by MCU by spi bus, and ADC passes through Spi bus is connect with MCU, completes Analog-digital Converter in MCU.

The beneficial effects of the utility model are: compared to the prior art, the advantage of this programme is to adjust and can compile by MCU The output voltage Vbias of the bias voltage Vbias output circuit of journey, and amplification coefficient K is adjusted, thus by different trips or instead The feedback voltage equivalent of the potentiometer of angle is presented into the input range for meeting same group of ADC, this programme is compatible with The valve of different trips or feedback angle reduces anti-without using excessively high-precision ADC or the gear set of different magnification ratios The cost of current feed circuit.

Detailed description of the invention

Fig. 1 is the system schematic of the utility model；

Fig. 2 is the flow chart of this utility model MCU control Vbias and programmable amplifier amplification coefficient；

Fig. 3 is the circuit diagram of embodiment 1；

Fig. 4 is the circuit diagram of embodiment 2.

Specific embodiment

The technical solution of the utility model, but the protection scope of the utility model are described in further detail with reference to the accompanying drawing It is not limited to as described below.

As shown in Figure 1, 2,

A kind of valve feed circuit, the circuit include: bias voltage Vbias output module, export 0V~+V biased electrical Vbias is pressed, wherein 0V indicates that the voltage value of feed circuit output when valve dead-center position ,+V indicate valve full scale feed circuit Output valve；Amplifier module, the feedback voltage Vfb of valve feedback potentiometer is sent into programmable amplifier after subtracting Vbias, through putting Vadc is obtained after K times big, is entered into ADC and carries out Analog-digital Converter；MCU control circuit, for selecting bias voltage The output voltage amplitude of Vbias output module and the value of amplification coefficient K.

Before the configuration is made, first have to determine the control strategy of MCU, the present embodiment is described as follows MCU control strategy:

Bias voltage Vbias, amplification coefficient K, the amplification voltage Vadc_zero of valve stroke zero point, valve stroke full scale Amplification voltage Vadc_span determination method it is as follows:

S1: when defining bias voltage Vbias output minimum, K=1；

S2: control valve positions output pressure minimum, obtains feedback voltage Vfb _ zero of valve stroke zero point, is arranged Vbias=Vfb_zero-x；, using the minimum value Vfb_zero of feedback potentiometer output as bias voltage, while in order to meet row Journey demand avoids going beyond the scope, and the value of Vbias here should also be suitably lower than Vfb_zero, so Vbias=Vfb_zero- X, wherein x can value preferred scope be (0 ,+V/100), x value is lower in practice, and accuracy is higher.

S3: control valve positions output pressure maximum, obtains feedback voltage Vfb _ span of valve stroke full scale, gradually increases Big amplification coefficient K；

S4: as Vadc=K*(Vfb_span-Vbias) >=(+V-y), the value of amplification coefficient K is obtained, while determining ADC Input range the upper limit.When to avoid amplification factor K increase, programmable amplifier may export saturation, cause Vadc_ There is mistake in span, just obtains the maximum value of K before amplifier output saturation, is judged using Vadc >=(+V-y), y and programmable The Linear Amplifer range of amplifier is related, preferably settable y=0.1V；

S5: control valve positions output pressure minimum, and the value and Vbias of fixed K is constant, obtains valve stroke zero point Amplify voltage Vadc_zero=K*(Vfb_zero-Vbias)；

Actual opening valve degree=[(Vadc-Vadc_zero)/(Vadc_span-Vadc_zero)] * 100%.

In above-mentioned steps S3, K is gradually increased in arithmetic progression, and the tolerance of arithmetic progression is (0.001,0.1), and K tolerance takes It is worth that smaller obtained precision is higher, Vadc=K*(Vfb-Vbias) close to the input range of ADC, i.e. Vadc_zero=K*(Vfb_ Zero-Vbias) close to the lower limit of ADC input range, Vadc_span=K*(Vfb_span-Vbias) close to ADC input range The upper limit, listed theory is determined according to the parameter of user's self-setting close to being in this programme, such as on Vadc_span and ADC Difference between limit is 0.1 or 0.2 or 0.3, and its purpose is to make Vadc=K*(Vfb-Vbias) close to the input model of ADC It encloses, to improve the precision of detection to greatest extent.

By the control strategy of above-mentioned MCU with program form write-in MCU control chip, it is used in following embodiment as The control strategy of MCU, in order to further embody, the MCU in following embodiment is all made of the single-chip microcontroller conduct of 89C51 model MCU control core.

Embodiment 1

As shown in figure 3, as one embodiment, the valve feedback system by resistance R1, resistance R2, resistance R3, resistance R4, Resistance R5, resistance R6, resistance R7, resistance R8, resistance R9 constitute bleeder circuit as bias voltage Vbias output circuit, this point Totally 8 output voltages are as bias voltage Vbias for exporting VREF1 ~ VREF8 for volt circuit, and output voltage is from low to high gradually Increase, MCU by REF1_CPU, REF2_CPU, REF3_CPU control single-ended 8 channel variable connector 4051D selection VREF1 ~ By single-ended 8 channel variable connector 4052D selectively output bias voltage Vbias, realization can for one of them in VREF8, i.e. MCU Program Vbias.By resistance R10, resistance R11, resistance R12, resistance R13, resistance R14, resistance R15, resistance R18, resistance R19, Resistance R20, resistance R21, resistance R22, resistance R23 and amplifier constitute subtracter and programmable amplifier, and MCU passes through OP1_CPU, OP2_CPU controls two-way 4:1 multidiameter option switch and controls programmable amplifier, realizes programmable amplification factor K.

Embodiment 2

As shown in figure 4, as one embodiment, which is made of MCU, ADC, DCA, PGA, and MCU passes through Spi bus controls the Vbias of DAC output different voltages value, and PGA is configured to difference amplifier, the difference of Vfb and Vbias are put Vadc output is generated after big and gives ADC, and amplification factor is configured by MCU by spi bus.ADC is connected by spi bus and MCU It connects, completes Analog-digital Converter in MCU.Wherein DAC can be independent chip and complete DAC function, and such as DAC7512 can also make DAC function is internally integrated with MCU.PGA, DAC can be independent chip and complete PGA function, and PGA280, ADS1286 such as can be used Deng, it is possible to use PGA the or ADC function being internally integrated using MCU.

The above is only the preferred embodiment of the utility model, it should be understood that the utility model is not limited to herein Disclosed form, should not be regarded as an exclusion of other examples, and can be used for other combinations, modifications, and environments, and Can be in contemplated scope described herein, modifications can be made through the above teachings or related fields of technology or knowledge.And this field The modifications and changes that personnel are carried out do not depart from the spirit and scope of the utility model, then all should be in right appended by the utility model It is required that protection scope in.

Claims (6)

1. a kind of valve feed circuit, which is characterized in that the circuit includes:

Bias voltage Vbias output module exports 0V~+V bias voltage Vbias, wherein+V is identical as ADC reference voltage；

Amplifier module obtains Vadc for K times by Vfb-Vbias amplification, and wherein Vfb is the feedback electricity of valve feedback potentiometer Pressure；

ADC module, for Vadc to be carried out Analog-digital Converter；

MCU control circuit, for selecting the output voltage amplitude of bias voltage Vbias output module and the value of amplification coefficient K.

2. valve feed circuit according to claim 1, which is characterized in that the bias voltage Vbias output module by Multiple resistance constitute bleeder circuit, and the MCU selects the output voltage of bleeder circuit by single-ended multichannel variable connector.

3. valve feed circuit according to claim 2, which is characterized in that the amplifier module is by multiple resistance and fortune It puts and constitutes subtracter and programmable amplifier, the MCU controls amplification coefficient K by difference multi-channel digital analog switch.

4. valve feed circuit according to claim 3, which is characterized in that the bias voltage Vbias output module by Resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, resistance R8, resistance R9 constitute bleeder circuit and make For bias voltage Vbias output circuit, the bleeder circuit for export VREF1 ~ VREF8 totally 8 output voltages as biased electrical Vbias is pressed, output voltage is gradually increased from low to high, and for MCU by REF1_CPU, REF2_CPU, REF3_CPU control single-ended 8 is logical Road variable connector 4051D selects one of them in VREF1 ~ VREF8, i.e. MCU is selected by single-ended 8 channel variable connector 4052D Property output bias voltage Vbias, realize programmable Vbias；

The amplifier module by resistance R10, resistance R11, resistance R12, resistance R13, resistance R14, resistance R15, resistance R18, Resistance R19, resistance R20, resistance R21, resistance R22, resistance R23 and amplifier constitute subtracter and programmable amplifier, MCU pass through OP1_CPU, OP2_CPU control two-way 4:1 multidiameter option switch and control programmable amplifier, realize programmable amplification factor K.

5. valve feed circuit according to claim 1, which is characterized in that the bias voltage Vbias output module by MCU controls the Vbias that DAC exports different voltages value by spi bus.

6. valve feed circuit according to claim 5, which is characterized in that the amplifier module is configured to difference by GA Amplifier generates Vadc output and gives ADC after amplifying the difference of Vfb and Vbias, amplification factor passes through spi bus by MCU Configuration, ADC are connect by spi bus with MCU, complete Analog-digital Converter in MCU.