RU429U1 - Ultrasonic sensor for cold and hot water flow meter - Google Patents

Abstract

An ultrasonic sensor for a cold and hot water flow meter, containing a piezoceramic element with two electrodes, one of which is connected to the housing, and the other to the generator and receiver, a titanium membrane located in a cylindrical metal case and having acoustic contact with the piezoelectric element and water, a damper adjacent to the piezoelectric element from the side of the electrode having a conclusion to the generator, characterized in that the piezoelectric element is made of anisotropic piezoceramics with the parameters: electromechanical coupling coefficient and the thickness of the vibration mode K1 = 0.45 - 0.6, the electromechanical coupling coefficient of the radial vibration mode Kr = 0 - 0.05, the longitudinal piezoelectric sensitivity g33 = (40-100) (mV * M) / N, the variation of g33 in the range 125 ± 25 ° C is 3 - 10%, the mechanical quality factor of the thick mode of vibration is Sm / t / = 5 -10, the damper is made of a material with sound impedance Zd = (1.3 - 1.5) * 10 ^ 6 kg / m2 s , a groove is made in the lower part of the housing parallel to the membrane plane, in which two dielectric matching layers are placed with sound impedances Zc1 = (5.6 - 6.0) * 10 ^ 6 kg / m2s and Zc2 = (2.5 - 3.0 ) * 10 ^ 6 kg / m 2 with thicknesses hc1 = (lamda1 / 8) - (lamda1 / 4) and hc2 = (lamda2 / 8) - (lamda2 / 4), where lamda1,2 is the length of the acoustic waves in the layers, the groove depth is at the thickness of the two matching layers.

Description

Utility model ULTRASBUKSVSH DA.TCHSCH FOR FLOW METER

hot water and hot water

The device relates to ultrasonic technology and is designated for operation as part of ultrasonic flow meters of cold and hot water in pipelines with a diameter of up to 400 mm.

In the development of ultrasonic flowmeters of liquid substances in pipelines of various diameters, a pulse method of measuring the flow rate of a liquid has recently been preferred, which involves the use of two equivalent sensors in one acoustic channel / I /. In this method, it is of fundamental importance that the probing ultrasonic packets of paired sensors have a minimum duration.

Ultrasonic sensors for flowmeters manufactured in Russia, as a rule, piezomaterials of the type TsTS are used as the active element.

The closest set of essential features to the claimed one is an ultrasonic sensor / 2 / based on the piezomaterial TsGS-19/3 /, which is part of an ultrasonic flow meter with a calculating Acustron / model UZR-V /, designed to measure the flow of cold water in pressure pipelines with a diameter of 400 -1000 mm. The principle of operation of this flow meter corresponds to / I / and is based on a change in the propagation velocity of an ultrasonic signal in a moving medium depending on the value of the velocity component of this medium in the direction of propagation of the ultrasonic signal. The drawing and construction description of the known sensor is presented in the appendix to the application, where I is a membrane, 2 is a piezoceramic element in the form of a disk with a diameter of 20 mm and a thickness of 1.5 mm of material 1 | GS-19, 3 - damper, 4 Nut, 5 - housing , b - wire, 7 - gasket, 8 - seal, 9 flange, 10 - cover, II - gasket, IE -, 13 - cable, 14 - connector .; ,

The geometric dimensions of element 2 are selected based on their required sensor operating frequency / 1.4 MHz /. Damper 3 serves to

epoxy casting with filler. Housing 5 with an installed membrane is designed to protect the piezoelectric element from chemical and external influences. The principle of operation of the known sensor is to use the piezoelectric effect of element 2. When electric signals arrive at the piezoceramic sample electrodes, the piezoelectric element performs mechanical vibrations following changes in the applied field. These mechanical vibrations are transmitted through the membrane to the measured fluid and the excitation of ultrasonic waves in it. The electrical signal is supplied through wire 6 and the housing 5.

Studies of the acoustic parameters of the known sensor showed that the duration of the probe packet in it (18 ISS; voltage sensitivity, determined by the ratio of the amplitude of the maximum echo pulse to the exciting vm signal for a time equal to three oscillation periods, to the first positive echo amplitude, is 0, 4-0.5.

The disadvantages of the known ultrasonic sensor for the flow meter are:

-Long duration of the probe package, which does not allow measuring the water flow in pipes with a diameter of less than 400 mm;

-low resolution of information signals / the lower the resolution is considered higher /, leading to the complication of electronic signal processing circuits;

-low working temperature, not allowing to measure the flow of hot water;

-Loss of energy during radiation.

The TsGS-19 material used in the known sensor has the following parameters / 3 /: dielectric permeability Gz5 / 1470, electromechanical coupling coefficient of the thickness of the vibration mode K 0.49, radial vibration honey / Suo, mechanical quality factor of the thickest vibration mode / i (- f.) - ее more than 83, longitudinal piezoelectric module ШЗ 300. longitudinal piezosensitivity wBM piezoelectric:% for a5 strain 2.1-10, Curie temperature - not less than 0 ° С. In addition, the change in, in the temperature range / 125 - 25 / ° C - not less

.

; permitting the latest amplitude, the echo efficiency of the operation of the piezoelectric elements as emitters and receivers of acoustic signals is determined primarily by the parameters governing the piezoelectric effect equation.

For the one-dimensional case, i.e. a piezoelectric element in the form of a plate / disk / oscillating only in thickness, without other changes in shape, the inverse and direct piezoelectric effects are described in elementary form as follows / /

1. The reverse piezoelectric CT -A), where C. - applied / radiated / voltage;

A) U - change thick; SS-piezoelectric piezoelectric module

2, Direct piezoelectric effect - Ut n Us where

AJfe - change in thickness caused by external factors; Uc - voltage at the piezoelectric element / receiver / no load; / 7zz piezoelectric strain constant.

If we proceed from the pressure P, which causes a change in thickness, then the direct piezoelectric effect can be written in the form Ue - where c / is the thickness, and l is the piezoelectric pressure constant / piezoelectric sensitivity /. Therefore, in the radiation mode, an increase in s / s in the reception mode is necessary -

The coefficients of the electromechanical coupling HG /, in particular, K-, characterize the efficiency of the / kpd / conversion of mechanical deformation into electrical voltage and vice versa for a given piezoelectric material. Therefore, higher values of Ar provide greater converter efficiency.

Along with K-t: for the plate to oscillate in thickness, the coefficient Kp is of particular importance, since its value determines the usually undesirable fluctuations in interference. The value of Kp should be possibly smaller than / / the anisotropy of the piezoelectric parameters, expressed by the ratio / Q / ЛГуе - possibly greater than /, t, k, otherwise a part of the energy applied to excite the radiation; The detergent will be lost or even appear as an undesirable waveform in the plate as a hindrance. The larger the more, the emitter deviates from the originally accepted ideal behavior of the emitter, oscillating only in thickness. At 10, interference is minimal.

 .

-7also the mechanical quality factor d / mouth) /) those5 are higher, the smaller the mechanical losses in ferroceramics /. The value determines the bandwidth of the converter. To obtain short pulses, the natural mechanical vibrations of the plate must be well damped with a damper attached to the rear side. However, if the piezoelectric material has a low mechanical quality factor, then for many purposes it can be used without additional damping, which in turn increases the sensitivity. -7-X

Equally important is the dielectric constant -SJ /. It determines the working frequency range / with decreasing Гз // the working frequency / increases /, provides electrical conditions / matching, and also determines the level of piezo-parschletra {Vjj -,

Based on the foregoing, it is clear that from the point of view of use in ultrasound: emitters and receivers, the TsTS-19 has insufficiently high values of Ls3,, insufficiently high anisotropy of the piezoelectric parameters K / A /, and not sufficiently low values (). In the specific case, when using the TsTS-19 in ultrasonic liquid flow meters, the low anisotropy of the piezoelectric parameters and the high mechanical quality factor do not allow obtaining a sufficiently short probe packet in the sensors, which makes it difficult to receive a pulse from a pair sensor, complicates its isolation and processing. Low parallels of ssLs cause low voltage sensitivity and resolution. Insufficiently high temperature stability does not allow determining the flow rate of hot water.

Thus, the disadvantages of the known sensor are due, primarily, to the use of piezoceramics I | TC-I9 as an active element, as well as the absence of special acoustic matching layers.

The purpose of creating the inventive ultrasonic sensor for a cold and hot water flow meter in pipelines with a diameter of up to 400} lm is to ensure the formation of short probed packets, increase the sensitivity of voltage, resolution, and stability of parameters in the temperature range / 125-25 /.

/ t / ff3)

 h. NOSES, without false fluctuations, which will lead to a significant simplification of the electronic circuit of the flow meter, expanding its functionality / control of hot and cold water /, reducing the size. The described technical result is achieved by the fact that in the known sensor for an ultrasonic water flow meter containing a piezoceramic element with two electrodes, one of which is connected to the housing, and the other is to the generator and receiver, a titanium membrane located in a cylindrical metal case and having acoustic contact with a piezoelectric element and water, a damper adjacent to the piezoelectric element from the side of the electrode connected to the generator, according to the claimed design, the piezoelectric element is made of an anisotropic piezo non-frames with parameters: - coefficient of electromechanical coupling of the thickness of the oscillation mode 0.45 t 0.6 coefficient of electromechanical coupling - radial mode of oscillation To t 0.05 - longitudinal piezoelectric sensitivity 4 ,, (40-100 11 - less in the interval (l25 - 25) ° С - (з -10}, -mechanical figure of merit with the thickness of the GiHLir vibration mode, the damper is made of a material with sound impedance Z (1.3 - 1.5) 10 kg / GM C, a groove is made in the lower part of the body parallel to the plane of the titanium membrane, in which there are two dielectric matching layers with sound impedance umi ((5,6 - 6, kG / (C) and bg (2,5 - 3, 10 kG / () and thickness c; /; e / --- and Leg 4 // 1 // A) - length acoustic waves in the matching layers /, the depth of the groove / 7 /, is equal to the thickness of the two matching layers. The inventive sensor for a hot and cold water flow meter is illustrated by the drawing in FIG. I. The ultrasonic sensor contains a piezoceramic element I with an electrode 2 and 3, a cylindrical metal housing 4, metallic; / titanium / membrane 5, the first matching layer 6 thickness -tg 9 the second matching layer 7 thickness Leia. Dg - de ldfer 8. The depth of the groove in which the akinetic layers are placed is. Electrode 2 connected / "

pin 9 to the generator / receiver /. The electrode 3 through the membrane 5 is connected to the housing 4. / Acoustic matching layers were selected experimentally. ≪ 2 s / d. And Ag / were calculated in accordance with / 5 / and / 6.7 //.

To measure the flow rate, the sensor is placed in an acoustic channel and is excited by an electrical impulse, which is supplied to the electrodes 2 and 3 of the element I. The piezoelectric element performs mechanical vibrations, which are through the LEM and E; skinny acoustic layers 6,7 are transferred to water and excite ultrasonic waves in it. The same sensor at the corresponding time receives an ultrasonic signal from a pair of sensors located in the same acoustic channel in accordance with the pulse method for determining the fluid flow rate. The ultrasonic signal through acoustic matching layers 7 and 6, the membrane 5 is fed to the piezoelectric element I, is converted as a result of the previous piezoelectric effect into an electrical signal, which through pin 9 is fed to the receiver.

Table I shows the functional parameters of the sensor of the claimed design, in which the active element is made of anisotropic piezoelectric ceramics based on Zh77 general form l eTfOz-CalfO fSWf / l nf / Os additives / 8 /. The parameters of the piezoelectric elements and matching layers obtained experimentally corresponded to the above ranges of their values when describing the technical essence of the claimed utility model. Piezoelectric element with a diameter of 20 um and an operating frequency

zC-) 4 MHz, excited by a pulsed voltage of 10 V, duration 0.3 μs.

The acoustic parameters of the sensor were tested in laboratory conditions when irradiated with water, at a depth of 100 mm. In fig. 2 shows the probillograms of the probe packet and the echo signal corresponding to example 4 in table I.

The implementation of a piezoelectric element from anisotropic piezoceramics with the specified set of parameter intervals / Q, Кр, OifiU) using two agreed acoustic layers with certain values of 2. and ht, the use of a damper with the indicated leads, as can be seen from Table I, to the following level of the functional parameters of the sensors:

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High temperature stability jB range ° C extends the operating temperature range up to 150 C.

All this, in turn, ensures the achievement of the technical result indicated in the description, namely; the formation of shorter (in comparison with the prototype) probing pulses, obtaining greater sensitivity / and resolution D, the ability to control the flow of hot water in the pipelines.

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Information sources

1.Golyamin I.P., Ultrasound., M, Publishing House Soviet Encyclopedia, 1979, 400 p.

2. Ultrasonic flowmeter with Ak stron counter. Model UZR-V. Technical description 2.82S.OOI TO. 1987.

3. OST 11044-87 Piezo materials and pure. Technical conditions M., 1987, 141 p.

4. Krautkremer I., Krautkremer G. Ultrasonic control of materials. Handbook M, Metallurgy, I99I, 752 pp.

5. Physical Encyclopedic Dictionary, M. Publishing House Soviet Encyclopedia, 1965, Vol. 4, 224 pp.

6. Skuchek E. Fundamentals of acoustics M. Publishing house Mir, 1976, v. 1. from. 421438

7. Ermolov I.N. Theory and Practice of Ultrasonic Testing M, Mechanical Engineering Publishing House, I98I, 239 pp.

8.K .. (p / Piezoelectric ceramic material Grineva L.D., Razumovskaya O.N., Shroshnichenko E.S., Shilkina L.A. Publ. In B.I. 30.a.i, W-.

- / 3

Claims (1)

An ultrasonic sensor for a cold and hot water flow meter, containing a piezoceramic element with two electrodes, one of which is connected to the housing, and the other to the generator and receiver, a titanium membrane located in a cylindrical metal case and having acoustic contact with the piezoelectric element and water, a damper adjacent to the piezoelectric element from the side of the electrode having a conclusion to the generator, characterized in that the piezoelectric element is made of anisotropic piezoceramics with the parameters: electromechanical coupling coefficient and the thickness of the vibration mode K1 = 0.45 - 0.6, the electromechanical coupling coefficient of the radial vibration mode Kr = 0 - 0.05, the longitudinal piezoelectric sensitivity g33 = (40-100) (mV * M) / N, the variation of g33 in the range 125 ± 25 ° C is 3 - 10%, the mechanical quality factor of the thick mode of vibration is Sm / t / = 5 -10, the damper is made of a material with sound impedance Zd = (1.3 - 1.5) * 10 ^ 6 kg / m2 s , a groove is made in the lower part of the body parallel to the membrane plane, in which two dielectric matching layers are placed with sound impedances Zc1 = (5.6 - 6.0) * 10 ^ 6 kg / m2s and Zc2 = (2.5 - 3.0 ) * 10 ^ 6 kg / m 2 with thicknesses hс1 = (lamda1 / 8) - (lamda1 / 4) and hc2 = (lamda2 / 8) - (lamda2 / 4), where lamda1,2 is the length of the acoustic waves in the layers, the depth of the groove at the thickness of the two matching layers.