CN2090518U - Stress type vortex street flow transmitter - Google Patents

Abstract

Disclosed is a stress type vortex street flow sensor which is a fluid oscillating device designed by the theory of Karman vortex street. The utility model has the advantages of improved signal characteristics in small flow measurement, low flow lower limiting value, wide measuring range ratio, and wide application. The utility model is characterized in that the probe body of the piezoelectric elements is respectively connected with a two-point feedback type differential electric charge amplifier, a conditioning amplifier with low frequency lift, a two-stage band pass filter, a single limit voltage comparator, a voltage follower, and a voltage stabilizer. As a result, the problem that low-frequency vortex street signals can not be correctly taken out in the process of small flow measurement is solved.

Description

Stress type vortex street flow transmitter

The utility model belongs to the flow measurement field in the instrument and meter for automation.Be a kind of fluid oscillation formula instrument of making according to the Karman vortex street principle design specifically.It is adapted to the flow measurement of liquid, gas and steam.

Present applied stress-type vortex street flow sensor is made up of parts such as housing, vortex generation body, piezoelectric element sonde body and detecting amplifiers.The subject matter of this sensor is: it is poor to measure the primary flow signal characteristic, and the flux lower limit value is higher and range is narrow.Its problem at first is the differential charge amplifier in the detecting amplifier, and its lower-cut-off frequency is too high, does not reach the requirement of low discharge vortex signal low-limit frequency; Next is the second-order low-pass filter in the detecting amplifier, and its gain is on the low side, does not satisfy the requirement of vortex signal amplitude versus frequency characte in the broad flow range.The problems referred to above cause the stress-type vortex street flow sensor of prior art, and low discharge low frequency vortex signal detects not come out, and can not correctly handle the vortex signal in the wide flow range.

The purpose of this utility model provides and has a kind ofly improved measurement primary flow signal characteristic, and the flux lower limit value is low, a kind of stress-type vortex street flow sensor that range ratio is wide and scalable.

For finishing above-mentioned purpose, the technical scheme that is adopted is according to Karman vortex street principle, vortex stress-type detection formula and piezoelectric element sonde body characteristic, redesign detecting amplifier.At first adopt two point reaction type differential charge amplifier and have the circuit form that the modification amplifier of bass boost combines, solve the prior art differential charge amplifier and be difficult to the problem that realizes that lower-cut-off frequency is low; Overcome use high input impedance (10 simultaneously ¹⁰Ω) the caused coupling of amplifier and high value feedback resistance difficulty, poor anti jamming capability, noise and the big shortcoming of drift.The circuit form that next adopts two-stage bandpass filter to be in series solves the prior art second-order low-pass filter and is difficult to accomplish the high problem that gains; By select tape bandpass filter parameter value, the amplitude versus frequency characte that two-stage series connection is obtained, basic symbols are combined in the amplitude versus frequency characte of vortex signal in the broad flow range.The 3rd adopts single limit voltage comparator, can be output as low level when not having signal; By selecting thresholding width magnitude of voltage, to stop various interference and noise to greatest extent.Other auxiliary circuit provides the central potential of circuit at different levels as adopting voltage follower, adopts voltage stabilizer can select supply voltage more flexibly.

Detecting amplifier parts of the present utility model are described in detail in conjunction with the accompanying drawings:

Figure one is a detecting amplifier block scheme of the present utility model;

Figure two is a detecting amplifier schematic diagram of the present utility model.

Shown in figure one, detecting amplifier of the present utility model has the modification amplifier of bass boost by two point reaction type differential charge amplifier, two-stage bandpass filter, and single limit voltage comparator, circuit such as voltage follower and voltage stabilizer constitute.Its input end d, e connect two extension lines of piezoelectric element sonde body YD, output terminal output voltage pulse signal

, give Flow Measurement Display Meter, and provide direct supply voltage DC to detecting amplifier by it.

Shown in figure two, the two point reaction type differential charge amplifier of detecting amplifier of the present utility model is by resistance R 1～R5, capacitor C 1～C5, and amplifier IC10P-07E/C and IC2 1/4LM124 form.The two point feedback is also used amplifier IC2 simultaneously except negative feedback, resistance R 3～R5, and the phase inverter output that capacitor C 5 is formed is to the in-phase end feedback of amplifier IC1.The sort circuit form can suppress the various common mode interference compositions that mix in the charge signal to greatest extent, strengthens the antijamming capability of test macro.Modification amplifier with bass boost is by resistance R 6～R8, capacitor C 6, C7, and current potential W and amplifier IC3 1/4LM124 form, and belong to homophase operational amplifier form.Its amplitude versus frequency characte is:

$\mathrm{KF}\left(f\right)=\frac{R_7+W}{R_7+\mathrm{aw}}[1+\frac{R_8/(R_7+w)}{\sqrt{1+{\left(\frac{f}{\mathrm{fo}}\right)}^2}}]----\left(1\right)$

In the formula: f ₀=1/ (2 π R ₈C ₇), a is the slip factor of potentiometer W, formula (1) is transferred the gain part for fitting before the bracket, with frequency-independent can be divided into two parts; In the bracket is the bass boost part, irrelevant with the adjusting gain.Two-stage bandpass filter is by resistance R 9～R12, capacitor C 8, C9, diode D1, D2 and amplifier IC4 1/4LM124, and resistance R 15～R17, capacitor C 11, C12, diode D3, D4 and amplifier IC5 1/4LM124 form, and belong to many ring feedback-type filter form.Different is, because of getting low-quality factor value, has removed sample and should be connected on resistance on resistance R 9 and capacitor C 8, C9 three's joining and the central potential, and when calculating, this goes sample resistance to get infinitely large quantity, and circuit performance is constant.Equally also remove sample and should be connected on resistance on resistance R 15 and capacitor C 11, C12 three's joining and the central potential.Resistance R 11 diode D1 and D2 and diode D3, D4 play the amplitude limit effect.Single limit voltage comparator is by resistance R 18～R21, and diode D5 and amplifier IC6 1/2LM158 form, and belong to the voltage comparator with descending lagging characteristics.Voltage follower is by resistance R 13, R14, and capacitor C 10 and amplifier IC7 1/2LM158 form.Voltage stabilizer is made up of capacitor C 13, C14 and three terminal integrated voltage stabilizer LM78L08.K switch is set, can selects the potential pulse of different high value.Diode D6 prevents that power supply DC from connecing anti-damage voltage stabilizer and be provided with.To the OV short circuit, can adopt two-wire system to take out current impulse the output voltage pulse ends.The also available series products of above-mentioned integrated device OP-07E/C, LM124, LM158 and LM78L08 substitutes.

The utility model stress-type vortex street flow sensor has solved the problem that the primary flow signal characteristic is poor, the flux lower limit value is higher and range is narrow of measuring.Correctly detecting low discharge low frequency vortex signal, and correctly handling under the prerequisite of the vortex signal in the wide flow range, accomplishing to suppress to greatest extent various low-and high-frequency and disturb and noise.

Two point reaction type differential charge amplifier of the present utility model and the circuit form that the modification amplifier with bass boost combines adapt to the Other Instruments instrument equally; The circuit form that two-stage bandpass filter is in series adapts to the vortex flow sensors of other model equally.

Claims (1)

1, a kind of stress-type vortex street flow sensor of forming by housing, vortex generation body, piezoelectric element sonde body and detecting amplifier parts, it is characterized in that the piezoelectric element sonde body connects two point reaction type differential charge amplifier, the modification amplifier with bass boost, two-stage bandpass filter, single limit voltage comparator, voltage follower, voltage stabilizer, a. two point reaction type differential charge amplifier is made up of resistance R 1～R5, capacitor C 1～C5, amplifier IC1op-07E/C and IC21/4LM124; B. the modification amplifier that has bass boost is made up of resistance R 6～R8, capacitor C 6 and C7, potentiometer W and amplifier IC31/4LM124; C. two-stage bandpass filter is by resistance R 9～R12, capacitor C 8 and C9, diode D1 and D2, amplifier IC41/4LM124, and resistance R 15～R17, capacitor C 11 and C12, diode D3 and D4, amplifier IC51/4LM124 form; D. single limit voltage comparator is made up of resistance R 18～R21, diode D5, amplifier IC61/2LM158.

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