CN201467080U - High-precision twin differential potentiometer feedback circuit - Google Patents

Abstract

The utility model relates to a high-precision twin differential potentiometer feedback circuit; in the circuit, one end of the potentiometer RS1 and one end of the potentiometer RS2 are connected with VCC, and the other end of the potentiometer RS1 and the other end of the potentiometer RS2 are grounded, a central tap of the potentiometer RS1 is respectively connected with one end of a capacitor C3 and one end of a resistance RC4 by a resistance RC3, the other end of the resistance RC4 is connected with one end of a capacitor C4 and one end of a resistance R2, the other end of the resistance R2 is connected with one end of the resistance R4 and the reverse input end of the pin 6 of a differential operational amplifier U1B, and the other ends of the capacitor C3 and the capacitor C4 and the other end of the resistance R4 are grounded respectively; a central tap of the potentiometer RS2 is respectively connected with one end of a capacitor C1 and one end of a resistance RC2 by a resistance RC1, the other end of the resistance RC2 is connected with one end of a capacitor C2 and one end of a resistance R1, the other end of the resistance R1 is connected with one end of a resistance R3 and the positive input end of the pin 5 of the differential operational amplifier U1B, and the other end of the resistance R3 is connected with the output end of the pin 7 of an operational amplifier circuit U1B, and the other ends of the capacitor C1 and the capacitor C2 are respectively grounded. By adopting the design, the precision of a positioner can be directly improved to 0.5 percent, the reliability is high and the anti-jamming capacity is high; the effect of the utility model is obvious when being applied to an EPA valve positioner, and the real-time high-precision requirement can be met.

Description

High accuracy duplex differential potential device feedback circuit

Technical field

The utility model relates to a kind of electronic circuit of instrument and meter for automation, particularly a kind of in automatically control or instrument and meter circuit the high accuracy duplex differential potential device feedback circuit of closed loop valve type control especially.

Background technology

In the circuit of automatic control or instrument and meter, especially the closed loop valve type is controlled, and often runs into the acquisition problems of position feedback.Most on the market at present valve positioners still adopt common potentiometer as feedback loop, and minority uses photoelectric encoder as feedback loop; Non-linear through the wearing and tearing of regular meeting's appearance potential device, potentiometer when using common potentiometer, thus the precision of potentiometer is affected, whole precision and the control effect that reduces instrument, the feedback loop of valve positioner commonly used.As shown in Figure 2; potentiometer directly enters the A/D Acquisition Circuit of single-chip microcomputer by following of amplifier by the RC Filtering Processing; guarantee under the linear situation at potentiometer; this circuit can be accomplished Linear Control; but on-the-spot industrial and mineral environment is abominable, often has the interference of power frequency or other electric fields, unavoidably influences the precision and the linearity of potentiometer; but there is not the measure of necessary anti-interference and raising precision in this circuit, belongs to more common popular circuit.The precision that improves locator has only from software and starts with.The software aspect adds measures such as necessary Filtering Processing or linearisation, can improve certain control precision, but because the restriction of hardware, can fundamentally not improve the precision and the control stability of locator.

Summary of the invention

Deficiency in view of the prior art existence, the utility model provides a kind of employing duplex differential potential device structure, and adopt Order RC filtering, and effectively improve the precision of gathering, enter the high accuracy duplex differential potential device feedback circuit of the A/D collection of single-chip microcomputer by differential operational amplifier.

The utility model for achieving the above object, the technical scheme of being taked is, a kind of high accuracy duplex differential potential device feedback circuit, it is characterized in that: comprise potentiometer RS1, RS2, resistance R C1, RC2, RC3, RC4, R1, R2, R3, R4, capacitor C 1, C2, C3, C4, differential operational amplifier U1B, described potentiometer RS1, RS2 one termination VCC, other end ground connection, centre cap connecting resistance RC3 one end of potentiometer RS1, the end of another termination capacitor C 3 of resistance R C3 and resistance R C4, another termination capacitor C 4 of resistance R C4 and an end of resistance R 2, other end connecting resistance R4 one end of resistance R 2 and the 6 pin reverse input ends of differential operational amplifier U1B, wherein capacitor C 3, C4, the other end of resistance R 4 is ground connection respectively, centre cap connecting resistance RC1 one end of potentiometer RS2, another termination capacitor C 1 of resistance R C1 and the end of resistance R C2, another termination capacitor C 2 of resistance R C2 and resistance R 1 one ends, the 5 pin positive input terminals of resistance R 1 other end connecting resistance R3 one end and differential operational amplifier U1B, resistance R 3 another termination discharge circuit U1B7 pin outputs, capacitor C 1, the C2 other end is ground connection respectively.

The beneficial effects of the utility model are: adopt the design of duplex differential potential device, under the situation that does not increase system cost, (do not adopt photoelectric encoder) and can improve equally the precision of system, and be 2 times raising, the precision of present most locator is all in 1%, and design of the present utility model can make the precision of locator directly bring up to 0.5%, and reliability height, antijamming capability are stronger; Use in the EPA valve positioner, effect is obvious, can satisfy the requirement of real-time high-precision.

Description of drawings

Fig. 1 is the utility model circuit diagram and as Figure of abstract.

Fig. 2 is the feedback loop figure of the valve positioner of prior art.

Embodiment

As shown in Figure 1, high accuracy duplex differential potential device feedback circuit, comprise potentiometer RS1, RS2, resistance R C1, RC2, RC3, RC4, R1, R2, R3, R4), capacitor C 1, C2, C3, C4, differential operational amplifier U1B, at both direction valve position feedback potentiometer RS1 is installed, RS2, when rotating, valve can drive a potentiometer RS1 forward rotation, a potentiometer RS2 backward rotation, vcc is provided by system, or by the inner generation of A/D, the termination vcc of potentiometer Rs1, other end welding system ground, equally, the termination vcc of resistance R s2, other end welding system ground, centre cap connecting resistance RC3 one end of potentiometer RS1, the end of another termination capacitor C 3 of resistance R C3 and resistance R C4, another termination capacitor C 4 of resistance R C4 and an end of resistance R 2, other end connecting resistance R4 one end of resistance R 2 and the 6 pin reverse input ends of differential operational amplifier U1B, its capacitor C 3, C4, the other end of resistance R 4 is welding system ground respectively, centre cap connecting resistance RC1 one end of potentiometer RS2, another termination capacitor C 1 of resistance R C1 and the end of resistance R C2, another termination capacitor C 2 of resistance R C2 and resistance R 1 one ends, the 5 pin positive input terminals of resistance R 1 other end connecting resistance R3 one end and differential operational amplifier U1B, the 7 pin outputs of resistance R 3 another termination discharge circuit U1B and the A/D of single-chip microcomputer gather inlet, capacitor C 1, the C2 other end is welding system ground respectively, forms the differential feedback potentiometer feedback amplifier of duplex thus.

In the differential amplifier circuit design, the influence for compensation bias current and drift should make

For making common-mode gain is zero, should make

Deriving the non-essential resistance pass by top two formulas is: R1=R3, R2=R4, closed loop gain

Circuit equivalent input resistance: Rsrd=2R1, the differential-type circuit has the subtraction function, and shortcoming is that input impedance is low, and common-mode rejection ratio is not high, so selected Aid and the bigger integrated transporting discharging of Kcmr for use.

Differential amplifier circuit detects this variation and sends into A/D and gather, and what deserves to be mentioned is that this circuit can make the variable quantity of potentiometer increase and be twice, and has strengthened excursion like this, and corresponding precision can double; And the interference of the second-order filter circuit filtering appts of being made up of the RC circuit improves antijamming capability;

With the potentiometer of two same-types install in the opposite direction with same kinematic axis on, the variation of potentiometer respectively changes identical amount to both direction.

The output computing formula of circuit is as follows:

$U0=(\frac{\mathrm{<figure-callout\; id="1"\; label="Vcc\; Rs"\; filenames="H2009200983233E00021.png"\; state="\{\{state\}\}">Vcc</figure-callout>}}{\mathrm{Rs}}\&times;\mathrm{\&Delta;<figure-callout\; id="1"\; label="k"\; filenames="H2009200983233E00021.png"\; state="\{\{state\}\}">k</figure-callout>}1+\frac{\mathrm{<figure-callout\; id="2"\; label="Vcc\; Rs"\; filenames="H2009200983233E00011.png,H2009200983233E00021.png"\; state="\{\{state\}\}">Vcc</figure-callout>}}{\mathrm{Rs}}\&times;\mathrm{\&Delta;k}2)\&times;\frac{R3}{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009200983233E00021.png"\; state="\{\{state\}\}">R</figure-callout>}1},$ Because Rs1 equals Rs2, Δ k1 equals Δ k2,

Above-mentioned formula is:

R3 equals R1,

Formula 2 clearly, the variation of resistance has increased one times;

Rotated 1K such as one, and another equally also rotates 1K, difference has just become 2K, the variable quantity that ratio obviously is doubled when installing one, in the filter circuit of back, adopt Order RC filtering, remove burr and on-the-spot electric field disturbed condition effectively, both realized with the differential amplifier circuit that 27L2 forms that the isolation of signal had also realized the amplification of signal, amplified the A/D conversion that output enters single-chip microcomputer.

Operation principle: the position feedback circuit that has adopted duplex differential potential device, with two identical feedback potentiometers with opposite direction connect with the valve location axle on, like this when valve location changes, a potentiometer clockwise rotates, another potentiometer rightabout rotates, the difference of potentiometer increases when only installing one and is twice, so the precision that A/D gathers can double.

Claims (1)

1. high accuracy duplex differential potential device feedback circuit, it is characterized in that: comprise potentiometer RS1, RS2, resistance R C1, RC2, RC3, RC4, R1, R2, R3, R4, capacitor C 1, C2, C3, C4, differential operational amplifier U1B, described potentiometer RS1, RS2 one termination VCC, other end ground connection, centre cap connecting resistance RC3 one end of potentiometer RS1, the end of another termination capacitor C 3 of resistance R C3 and resistance R C4, another termination capacitor C 4 of resistance R C4 and an end of resistance R 2, other end connecting resistance R4 one end of resistance R 2 and the 6 pin reverse input ends of differential operational amplifier U1B, wherein capacitor C 3, C4, the other end of resistance R 4 is ground connection respectively, centre cap connecting resistance RC1 one end of potentiometer RS2, another termination capacitor C 1 of resistance R C1 and the end of resistance R C2, another termination capacitor C 2 of resistance R C2 and resistance R 1 one ends, the 5 pin positive input terminals of resistance R 1 other end connecting resistance R3 one end and differential operational amplifier U1B, resistance R 3 another termination discharge circuit U1B7 pin outputs, capacitor C 1, the C2 other end is ground connection respectively.

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