RU430U1 - 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 a generator and a receiver, a titanium membrane located in a cylindrical metal housing and having acoustic contact with the piezoelectric element, a damper adjacent to the piezoelectric element from the side of the electrode having an output to the generator, characterized in that the active piezoceramic element consists of two half disks, the first half disk is made of piezoceramics with steam etrami: electromechanical coupling coefficient of thickness vibration mode Kt = 0.45 - 0.55; the longitudinal piezoelectric module d33 = 300 - 400 pC / H, the change in d33 in the temperature range 125 ± 25 ° C is 5 - 10%, the mechanical quality factor of the thick vibration mode Qm (t) = 10 - 30, the second half-disk is made of piezoceramics with parameters: coefficient the electromechanical coupling of the thick vibrational mode Kt = 0.45-0.6, the coefficient of electromechanical coupling of the radial vibrational mode Kp = 0-0.05, the longitudinal piezoelectric sensitivity g33 = (40-100) mVm / N, the change in g33 in the temperature range 125 ± 25 ° C is 3 - 10%, the mechanical quality factor of the thick mode of vibration Qm (t) = 5 - 10, damp p is made of a material with sound impedance Zd = (1.3 - 1.5) * 10 ^ 6 m2 * s, a groove is made in the lower part of the body parallel to the plane of the titanium membrane, in which two dialectic matching layers with sound impedances Zc1 = ( 5,6 - 6,0) * 10 ^ 6 kg / m2 * c and Zc2 = (2,5 - 3,0) * 10 ^ 6 kg / m2 * c and thickness hc1 = (lamda1 / 8) - (lamda1 / 4) and hc2 = (lamda2 / 8) - (lamda2 / 4), where lamda1, lamda2 are the lengths of acoustic waves in the matching layers, the depth of the groove Hn is equal to the thickness of the two matching layers.

Description

Utility model ULTRASH OVES SENSOR FOR FLOW

colder AND HOT water The device relates to ultrasonic technology and is designed to operate as part of ultrasonic flow meters of cold and hot water and pipelines with diameters from 400 to 1000 mm.

When developing ultrasonic flowmeters of liquid substances in pipelines of various diameters, a pulsed method of measuring the fluid flow rate has recently been preferred, which involves the use of two equivalent sensors in one acoustic channel / I /. In such a method, it is crucial that the probing ultrasonic packets of paired sensors have a minimum duration.

Ultrasonic sensors for flow meters manufactured in Russia, as a rule, use PZT type piezomaterials as an active element.

The closest set of essential features to the claimed one is an ultrasonic sensor / 2 / based on the piezomaterial TsTS-19/3 /, which is part of an ultrasonic flow meter with an Acustron counter / model UZR-V /, designed to measure cold water flow 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 companion speed of this medium in the direction of ultrasonic propagation

signal. ,. ,

"5 ........ " , , . . .l.

The drawing and construction description of the known sensor are presented in the appendix to the application, where t is a membrane, 2 is a piezoceramic element in the form of a board with a diameter of 20 1 Ш and a thickness of mm made of TsGS-19 material, 3 is a damper, 4 is a nut, 5 is a housing, b is wire, 7 - gasket, 9 - flange, 10 - cover, II - Щ) oklada, 12 nut, 13 - cable, 14 - connector. I

The geometric dimensions of the element 2 are tiibpalDl,% (p: one of the required operating frequency of the sensor / 1.4 MHz /. Damper 3 serves to

the formation of short emitted pulses and is an epokeid resin filled with filler. Case 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 dielectric effect of element 2. Upon receipt of electrical signals by 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 liquid and excite ultrasonic waves in it. The electrical signal is supplied through the wire 6 and the housing 5,

Studies of the acoustic parameters of the known sensor showed that the duration of the probe package in it / is 18 microns; voltage sensitivity, determined by the ratio of the amplitude of the maximum echo-pulse to the excitation. / V to the schwalva, is -; resolution

the ability l representing the ratio of the last amplitude of the echo in a time equal to three periods of oscillation, to the first positive amplitude of the echo, is 0.4 -0.5,

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

- the long duration of the probe packet, making it difficult to receive a pulse from a pair of sensors, complicating its selection and processing;

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

-low working temperature Te ° C /, not allowing to measure the flow of hot water;

-Loss of energy during radiation. ;

ShchS-19 material used in the known sensor, following parameters / 3 /: dielectric constant Гз5 / а а 1470, electromechanical coupling coefficient of the thick vibrational mode Kt - 0.49, radial vibrational mode - Кр "0.47, mechanical quality factor of the thick mode fluctuations (YaubO ® more

longitudinal piezomodule s / sz ZSYu S, center-end sensor - -, ci. 23, piezoelectric to | 1 Zhvnstanta. deformations

АЗЗ «2.1 10 -, Curie temperature - not less than 290 С, In addition, the change in the temperature range / 125 - 25 / ° С is not less than 10 96,

The effectiveness of the piezoelectric elements as emitters and receivers of acoustic signals is determined primarily by the parameters included in the equation of the piezoelectric effect.

For the odeomer 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 effect -4) 6, where and is the applied / emitted / voltage, the change in thickness,

C / 3S - piezoelectric piezoelectric module.

2, Direct piezoelectric effect - Ue - hzz Ye, where

D / (change in thickness caused by external factors,

1 voltage on the piezoelectric element / receiver / no load,

 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 / X 0 - /} -, where c / is the thickness, sz is the piezoelectric pressure constant / piezoelectric sensitivity /. Therefore, in the radiation mode, an increase in r / s is necessary, in the reception mode,% j (h s).

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

Along with / C, the coefficient / y is of particular importance for plate vibrations in thickness, since its value usually determines undesirable fluctuations in interference, and the ratio should be as small as possible compared to / the anisotropy of the piezoelectric parameters, expressed as a ratio possibly larger than /, t, k. otherwise, part of the energy applied to excite the emitter will be lost or even appear as an undesirable waveform in the plate as a hindrance. The larger f / y &, the stronger the deviation of the emitter from the originally accepted ideal behavior of the emitter, oscillating only in thickness. With / C / L UY, interference is muxed.

In addition to piezoelectric constants, the mechanical quality factor is also decisive, the higher, the lower the mechanical loss in ferroceramics /. The value (determines the bandwidth of the transducer. To obtain short pulses, the intrinsic mechanical vibrations of the plate should be well damped by 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 sensitivity.

The dielectric constant is no less important (it determines the working frequency range / with decreasing cSF / fc, the working frequency increases /, provides the conditions for electrical matching, and also determines the level of piezoelectric parameters

/ fjJ

Based on the foregoing, it is clear that from the point of view of use in ultrasonic emitters and receivers, the TsTS-19 has not high enough values, f, not very high anisotropy of the piezoelectric parameters I /, not enough low values / fo) In the specific case when using the TsTS-19 in ultrasonic liquid flow meters , low anisotropy of the piezoelectric parameters, rather high mechanical Q factor do not allow to obtain a sufficiently short probe packet in the sensors, which makes it difficult to receive a pulse from a pair snip complicates its isolation and handling. Low parameters 33) cause low voltage sensitivity and resolution L. Insufficiently high temperature stability does not allow to determine the flow of hot water.

Thus, the disadvantages of the known sensor are primarily due to the use of TsGS-19 as an active element of piezoceramics, as well as to the absence of special acoustic matching layers.

The purpose of creating the inventive ultrasonic sensor for a flow meter of cold and hot water in pipelines with a diameter of 400 to 1000 mm is to ensure the formation of shorter probing packages, to increase the sensitivity of

-7

4.

voltage, resolution, stability of parameters in the temperature range up to + 150 ° С,

This will allow you to receive a high-intensity information signal without false fluctuations, which will lead to a significant simplification of the electronic circuit of the flow meter, expanded its functionality / control of cold and hot water /, reduce the size.

The described technical result is achieved by the fact that in the known sensor for an ultrasonic flow meter, the water contains a piezoceramic element with two electrodes, one of which is connected to the housing, and the other to the generator and receiver, a metallic membrane located in a cylindrical metal case and having acoustic contact with the piezoelectric element and water, a damper adjacent to the piezoelectric element on the side of the electrode having a terminal to the generator, according to the claimed design, the active piezoceramic element um of two half-disks, a first half-disc is made of piezoceramics with parameters:

coefficient of electromechanical coupling TOjrapiHHOE vibration modes / C 0.45 - 0.55

- longitudinal pyeaomodul "(ZOO - 400),

- the change in o / sv temperature range / 125 - 25 / ° C is / 5 - 10 /%

-mechanical figure of merit of a thick mode of vibrations

& Hi- 10 - 30,

the second half-disk VESHOLnen from piezoceramics with parameters:

is the coefficient of electromechanical coupling of the thick mode of oscillations / G - 0.45 - 0.6

-coefficient of electromechanical coupling of the radial mode of vibrations / С О - 0,05

- longitudinal piezosensitivity

At (40 - iwjaSJ, the change in the interval / 125 - 25 / ° C is / 3 - 10 /

-mechanical quality factor of a thick mode of vibrations

(ftvfi9 5-10,

the damper is made of material with sound resistance

/ 1/93 03 /

 a groove is made in the lower part of the case parallel to the plane of the titanium membrane, in which two dielectric matching layers are placed with sound impedances Zci (5.5 - StOj-IO kg / 2 ez. (2.5 - 3.0j-10 kg / (thickness - - - and - Tf / Л "; - the length of the acoustic waves in the matching layers /, the depth of the groove L / is equal to the thickness of the two concordant layers,

We declare the sensor of the day of the flow meter cold and hot water is illustrated by the drawing in Fig. I,

The ultrasonic sensor contains a piezoelectric element I in the form of a half-disk / 1/2) 20 mm / with electrodes 3 and 4, a piezoelectric element 2 in the form of a half-disk / 1/2 jD / 20 mm / with electrodes 5 and b, a cylindrical metal case 7, metal / titanium / membrane 8, the first acoustic matching layer 9 of thickness a - - y-, the second acoustic matching layer 10 of thickness jt damper II, Depth a, and in which the acoustic layers are placed is equal to he / g. The electrode is connected by terminal 12 to the generator, electrode 5 with the help of the 13th plug-in to the receiver. The electrodes 4 and b through the membrane 8 are connected to the housing 7, / The acoustic matching layers were selected experimentally, the values of Z and / were calculated in accordance with / 5 / and / 6,7 //,

To measure water flow, the sensor is placed in an acoustic channel and is excited by an electric pulse, which is supplied to the electrodes 3 and 4 of element I, the piezoelectric element performs mechanical vibrations, which are transmitted through the membrane 8 and matching acoustic layers 9, 10 to the water and excite ultrasonic waves in it. The same sensor at an appropriate time receives an ultrasonic signal from a pair of sensors located in the same acoustic channel in accordance with the pulse method of determining the fluid flow rate. The ultrasonic signal through the acoustic layers 10 and 9, the membrane 8 enters the piezoelectric element 2, is converted as a result of the direct piezoelectric effect into an electrical signal, which through terminal 13 enters the receiver,

In I, the parameters of the sensor of the claimed design are given, in which the first element in the form of a half-deck / 1/2 0 20 mm / is made of piezo-kazyazicheskoyBO material PKR-37 based on titanium / 3 iOSssL

 b

(and

S H 4D

Sat

-1

lead and zirconate with additives / 8 /, the second active element also in the form of a half-disk / 1/2 jS 20 mm / is made from an anisotropic piezoelectric ceramic material based on the general form - Ca TfO - with additives / 9 /. The parameters of the piezoelectric elements and matching layers obtained experimentally corresponded to the WB indicated intervals of their values when describing the technical nature of the claimed utility model. The first pieoelectric element in the form of a half-disk / 1/2 0 20 mm / s with a working resonant frequency of 7 g (0.14 MHz was excited by a pulse voltage of 20 V, duration 0.3 μs. The acoustic parameters of the sensor were checked under laboratory conditions when irradiated with water, depth of 400 hl The reflected ultrasonic vibrations were received by the second half-disk. Figure 2 shows waveforms of the sounding and echo sounding probes corresponding to example 4 in table I,

The execution of the first half-disk from piezoceramics with the specified set of intervals of the parameters X, g4j to the following level of functional acoustic parameters of the sensor:

/ (7-2

M 0.2 - 0.3

.) W Г - 14) ISS

high temperature stability o / 53 and in the range / 125 25 / C extends the working temperature range to 150 ° C. All this in turn ensures the achievement of the technical result indicated in the description, namely: the formation of shorter / probe pulses compared to the prototype, obtaining greater sensitivity and resolution, the ability to control the flow of hot water in the pipelines. Applicant applicants .iiA L. Slesareva,

Information sources

1.Golyamin I, P. Ultrasound., M. R1zd-in Soviet Encyclopedia, 1979, 400 p.

2. Ultrasonic flowmeter with Acustron counter. Model UZR-V. Technical description 2.833.001 TO. 1987 year

3. OST 11044-87 Piezoceramic materials. Specifications, M., 1987, 141 pp.

4. Krautkremer I. Krautkremer G. Ultrasonic control of materials. Directories, Metallurgy, I99I, 752 s,

5. Physical encyclopedic dictionary. M. Publishing House Soviet Encyclopedia, Щ65, Т, 4, 224 p.

6. Skuchik E, Fundamentals of Acoustics M. Publishing House Mir, 1976, T, 1, s, 421438.

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

8.Fesenko E, G., Danziger A, I ,, Razumovskaya O.N., Reznichenko L, A, Panich A, E., Grineva L, D. et al. Highly effective piezoceramic materials in Sat, Piezoactive materials, Physics, technology, application in devices. Rostov-on-Don, Publishing House of Rostov University. , I99I. s, 5-14.

9.A.S. Piezoelectric ceramic material / Grineva L, D ,, Razumovskaya 0, N ,, Miroshnichenko E, C ,, Nshkina L.A. - Publ., In B, I, ZL / J. / R

-1 // / $ 3 0 35 // D

thirteen.

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 a generator and a receiver, a titanium membrane located in a cylindrical metal housing and having acoustic contact with the piezoelectric element, a damper adjacent to the piezoelectric element from the side of the electrode having an output to the generator, characterized in that the active piezoceramic element consists of two half disks, the first half disk is made of piezoceramics with steam etrami: electromechanical coupling coefficient of thickness vibration mode Kt = 0.45 - 0.55; the longitudinal piezoelectric module d33 = 300 - 400 pC / H, the change in d33 in the temperature range 125 ± 25 ° C is 5 - 10%, the mechanical quality factor of the thick vibration mode Qm (t) = 10 - 30, the second half-disk is made of piezoceramics with parameters: coefficient the electromechanical coupling of the thick vibrational mode Kt = 0.45-0.6, the coefficient of electromechanical coupling of the radial vibrational mode Kp = 0-0.05, the longitudinal piezoelectric sensitivity g33 = (40-100) mVm / N, the change in g33 in the temperature range 125 ± 25 ° C is 3 - 10%, the mechanical quality factor of the thick mode of vibration Qm (t) = 5 - 10, damp p is made of a material with sound impedance Zd = (1.3 - 1.5) * 10 ^ 6 m2 * s, a groove is made in the lower part of the body parallel to the plane of the titanium membrane, in which two dialectic matching layers with sound impedances Zc1 = ( 5.6 - 6.0) * 10 ^ 6 kg / m2 * c and Zc2 = (2.5 - 3.0) * 10 ^ 6 kg / m2 * c and thickness hc1 = (lamda1 / 8) - (lamda1 / 4) and hc2 = (lamda2 / 8) - (lamda2 / 4), where lamda1, lamda2 are the lengths of acoustic waves in the matching layers, the depth of the groove Hn is equal to the thickness of the two matching layers.