SU1436280A1 - Method and apparatus for determining the response of piezoelectric irradiators at the second harmonic - Google Patents

Abstract

The invention relates to acoustic measurements and can be used to determine and monitor nonlinear distortions of piezoelectric sound emitters by measuring the sensitivity at the second harmonic. The purpose of the invention is to increase the measurement accuracy. The excitation of the sound source is carried out in such a way as to ensure equality of the amplitudes and the opposite of the phases of the acoustic pressure components at the excitation frequency. A first measurement of the amplitude and phase of the acoustic pressure component of the received signal at the second harmonic is made. Then, the excitation amplitude of the emitter under study is changed, and a second measurement of the amplitude and phase of the acoustic pressure of the component of the received signal at the second harmonic is performed. The sensitivity of the piezoelectric transducer is determined by the calculation formula given in the description. 2 sec. f-ly, 2 ill. i (L

Description

with

05

Yu

CX)

The invention relates to acoustic measurements and can be used to determine and control nonlinear distortions of piezoelectric sound emitters by measuring the sensitivity at the second harmonic.

The purpose of the invention is to increase the point

measurements.

FIG. I shows a vector diagram; in fig. 2 - a device that implements the proposed method.

The sensitivity on the second harmonic is determined by the formula

one

one

2P-jf / UH,

(I)

The amplitude of the acoustic pressure component of the incoming signal with a frequency of 2f.

electric excitation voltage amplitude of converter j under investigation; excitation signal frequency,

The simultaneous operation of two double frequency signals in ma can be represented in

-cos (-f t /)), (2)

de Ch and 1d

sensitivity on the second harmonic of the investigated and additional emitters;

If and (phase of the acoustic pressure component of the received signal with a frequency of 2f;

the emitter, it is necessary to find the vector difference modulus (the difference vector is shown in Fig. 1 by a bold arrow) As can be seen from FIG. one

tvUm7

2l

 tl

(3)

Hence, by expressing the vectors in approximate values, we obtain the formula for determining fj.

l

2CP, VP, - “P,

, (,

luL-yL /

WITH )

Formula (4) is valid for any amplitude-phase relations at the fundamental frequency, f,

To eliminate the mutual influence on the field of the studied and additional emitters, it is necessary to locate them at distances yy exceeding SL, where A is the wavelength corresponding to the frequency f. When measuring, it is necessary to ensure the minimal influence of the nonlinearity of the medium on the accuracy of determining the sensitivity at the second harmonic. Therefore, it is desirable to locate the receiving point closer to the radiator m.

A device that implements the method (Fig. 2) consists of a series-connected sinusoidal oscillator 1, a divider 2 often35

you, pulse modulator 3, re-

switchable divider 4, power amplifier 5 and emitter b, the output of pulse modulator 3 is connected to the input of series 40 40-adjustable delay line 7, jm- equal attenuator 8, second power amplifier 9 and additional radiator JO, second pulse modulator input 3 soybeans

and, and

Uma amplitudes of the voltage of the electron 45 Dinen with the first output of the generator of the critical excitation L of rectangular pulses, the second

the output of which is connected to the first input of the second voltmeter 12, whose input is connected to the output of the second 50 amplifier with filter 13, the input of the last one is connected to the receiver 14

investigated and additional emitters. At the point of reception, the amplitudes Pd are measured, and the phase C / Jj. acoustic pressure P2 (t). The vector diagram, shown in Fig. 2, is shown in FIG. one.

After changing the value of U

mi

the resulting amplitude is changed

acoustic pressure, which is also connected to the input of the amplifier with filter 15, the output of which is РР-2 and phase (acoustic pressure 55 of the keys to the input of the phase meter 16 and the volt-component of the received signal from meter 17, the third input of the phase meter 16 with a frequency of 2f ( figure 2) and the second input of the voltmeter 17

To isolate only the non-linear effect created by the subject.

the keys to the input of the phase meter 16 and the voltmeter 17, the third input of the phase meter 16 and the second input of the voltmeter 17 connect; Kena with the second output of the square pulse generator, the second

I 1

input phase meter 16 is connected to the output of the generator I sinusoidal oscillations.

The device works as follows.

When the power is turned on, the generator 1 of sinusoidal oscillations generates a signal with a frequency of 2f, which is fed to the second input of the phase meter 16 and to. the divider 2 frequency input, from the last output, a harmonic signal with a frequency f is fed to the first input of the pulse modulator 3. The square pulse generator 11 supplies the second pulse pulse modulator 3 to the second input, while the output pulse pulse modulator 3 forms radio pulses arriving at the input. the emitter 6 and the additional emitter 10. The acoustic signal received by the receiver 14 aKycT f4ecKoro pressure is fed to the measuring devices: the signal component with the main frequency - per voltmeter 12, the signal component with double frequency - per voltmeter 17 and phase meter 16. At that voltmeters 12 and 17 indicate the amplitude of the corresponding component, and on the phase meter the phase component of the acoustic pressure with a double frequency, measured at the steady-state portion of the received signal, which is achieved by a rectangular delay a pulse generated at the second output of a generator of 11 rectangular pulses relative to a pulse at its first output for a time equal to the time of transients plus the time of propagation of the wave from the emitters to the receiver. At the first stage of measurements, the selection of the attenuation coefficient of the controlled attenuator 8 and the delay time of the adjustable line

The 7 delays provide the minimum level of the main frequency signal for an agm anim voltmeter 12, then take the readings of the voltmeter 17 and the phase meter 16. In the second measurement step, set the switchable divider 4 to another position and take the readings of the voltmeter 17 and phase meter 16. Based on the data obtained, the sensitivity is calculated at the second harmonic of the radiator 6.

1436280

F o rm y. l

the invention

1. A method for determining the sensitivity on the second harmonic of piezoelectric emitters by exciting the emitter under study at frequency f, receiving an acoustic signal and measuring the amplitude of the acoustic pressure of the component of the received signal with a frequency of 2f, in order to increase the accuracy of sensitivity measurement on the second the harmonica is additionally excited by the second radiator at the frequency f, and the amplitude and phase of the electrical excitation signal are chosen from the condition of equality of amplitudes and ozhnosti phase was Yusch rx acoustic pressure with frequency f, produced under study and additional sources. At the receiving point, the first change in the amplitude and phase of the acoustic pressure of the component of the received signal with a frequency of 2f is then changed no more than twice the excitation amplitude of the emitter under study and the second measurement of the amplitude and the phases of the acoustic pressure of the component of the received signal with a frequency of 2f, the sensitivity at the second harmonic of the piezoelectric emitter is determined by the formula 2 g ICP. + PI-IP

(- 22

r / 2

where P, t.

and

mi

0

B

0

and

H.

eleven

hii

five

respectively, the result of the first measurement of the amplitude and phase of the acoustic pressure and the amplitude of the voltage of the electrical excitation of the investigated radiator at the first measurement,

respectively, the result of a second measurement of the amplitude and phase of the acoustic pressure and the amplitude of the voltage of the electric excitation of the investigated radiator in the second measurement.

five

2. A device for determining the sensitivity of the second harmonic of a piezoelectric emitter, containing in series: a sinusoidal oscillator, a pulse modulator, a power amplifier, an emitter, an acoustic pressure receiver connected in series, a filter amplifier, a voltmeter, and a square pulse generator connected to the voltmeter and The second input of the pulse modulator, characterized in that, in order to increase the accuracy of determining the sensitivity at the second harmonic, Frequency divider, switchable divider, phase meter, serially connected adjustable delay, controlled attenuator, second power amplifier and dt

806

An additional emitter, a second amplifier with a filter and a second voltmeter connected in series, the input of the frequency divider and the first input of the phase meter are connected to the output of the sinusoidal oscillator, the output of the frequency divider is connected to the input of the pulse modulator, the output of the pulse, modulator - with the input of a switchable divider and with the input of the adjustable delay line, the output of the switchable divider is connected to the input of the power amplifier, the input of the second amplifier with the filter is connected to the receiver of acoustic pressure, output One amplifier with a filter is connected to the second input of the phase meter, and the output of the square pulse generator is connected to the input of the second voltmeter and to the third input of the phase meter.

fpue. /

9lis.2

Claims (2)

Claim 1. A method for determining the sensitivity at the second harmonic of piezoelectric emitters by exciting the studied emitter at a frequency f, receiving acoustic sig When power is turned on, the generator 1 of the sinusoidal oscillations generates a signal with a frequency of 2f, which is fed to the second input of the phase meter 16 and on. the input of the frequency divider 2, from the output of the last harmonic signal with a frequency f is supplied to the first input of the pulse modulator 3. The rectangular pulse generator 11 supplies rectangular pulses to the second input of the pulse modulator 3, while the output pulses are generated at the output of the pulse modulator 3. the emitter 6 and the additional emitter 10. The acoustic signal received by the receiver 14 of the acoustic pressure is supplied to the measuring instruments: the signal component with the fundamental frequency is sent to the voltmeter 12, the signal component with the doubled frequency is sent to the voltmeter 17 and phase meter 16. Moreover, the voltmeters 12 and 17, the amplitude of the corresponding component is displayed, and on the phase meter, the phase of the acoustic pressure component with a double frequency, measured in the steady state of the received signal, which is achieved by the delay of the first pulse generated at the second output of the generator 11 of rectangular pulses relative to the pulse at its first output for a time equal to the time of transient processes plus the propagation time of the wave from the emitters to the receiver. At the first measurement stage, by selecting the attenuation coefficient of the controlled attenuator 8 and the delay time of the adjustable delay line .7, the minimum signal of the main frequency is provided by the readings of the voltmeter 12, then the voltmeter 17 and the phase meter 16 are read. At the second measurement stage, the switchable divider 4 is set to another position and take readings of the voltmeter 17 and phase meter 16. Based on the data obtained, the sensitivity at the second harmonic of the emitter 6 is calculated. For measuring the amplitude of the acoustic pressure of the component, the ^10th signal with a frequency of 2f is received, characterized in that, in order to increase the accuracy of measuring sensitivity at the second harmonic, the second emitter is additionally excited at a frequency f, the amplitude and phase of the electric excitation signal being chosen from the condition amplitudes and phase opposites of acoustic pressure components with a frequency! f created by the investigated and additional sources. kami at the receiving point, carry out the first change in the amplitude and phase of the acoustic pressure of the component of the received signal with a frequency of 2f, then change no more than two times the excitation amplitude of the studied emitter and conduct a second measurement of the amplitude and phase of the acoustic pressure of the component of the received signal with a frequency 2f, the sensitivity at the second harmonic of the piezoelectric emitter is determined by the formula, j l ./l ^V - ^u 4i where Ρ _Σ1 , U is, respectively, the result of the first measurement of the amplitude and. phases of acoustic pressure and amplitude 4S of the voltage of the electric excitation of the studied emitter during the first measurement, U _M2 is, respectively, the result of a second measurement of the amplitude and phase of the acoustic pressure and the amplitude of the voltage of the electric excitation of the emitter under study in the second measurement. 2. A device for determining the sensitivity at the second harmonic of piezoelectric emitters, comprising serially connected; a sine wave generator, a pulse modulator, a power amplifier, a radiator, a series-connected acoustic pressure receiver, an amplifier with a filter, a voltmeter and a square-wave generator connected to a voltmeter and to the second input pulse modulator, characterized in that in order to increase the accuracy of determining the sensitivity at the second harmonic, de frequency divider, switchable divider, phase meter, series-connected adjustable delay line, controlled attenuator, second power amplifier and additional radiator, series-connected second amplifier with filter and second voltmeter, with the input of the frequency divider and the first input of the phase meter connected to the output of the generator sinusoidal oscillations, the output of the frequency divider is connected to the input of the pulsed modulator 1 Q RA, the output of the pulse, modulator with the input of the switchable divider and the input of the adjustable line holders, the output of the switchable divider is connected to the input of the power amplifier15, the input of the second amplifier with the filter is connected to the acoustic pressure receiver, the output of the amplifier with the filter is connected to the second input of the phase meter, and the output of the generator is directly 20 carbon pulses connected to the input of the second voltmeter and to the third input phase meter. F1S2.2