SU1307256A1 - Device for measuring high-frequency pressure oscillations - Google Patents

Abstract

This invention relates to the measurement of the varying pressure of vapor, gas and fluids. The purpose of the invention is to expand the frequency range of measurements. For this, the device contains a monitored object 1, an accelerometer 2, an amplification and conversion circuit including an amplifier 3, a band filter 4, a recorder 5, a spectrum analyzer 6. Accelerometer 2 is mounted on an elastic element — a membrane that oscillates equivalent to vibrations. Amplitude — Measuring pressure oscillations is proportional to the amplitude of the measured vibration accelerations with a constant factor in the working frequency range. 2 Il. c & 1

Description

1.1

The invention relates to the measurement of the varying (oscillatory) pressure of vapor, gases and liquids, in particular to the measurement of high-frequency pressure fluctuations in pneumatic fluid systems.

The aim of the invention is to expand the frequency range of measurements of high-frequency pressure fluctuations.

Fig 1 shows the proposed device; in fig. 2 - amplitude-frequency characteristics (AFC) of the proposed device.

A device for measuring high-frequency pressure oscillations in the monitored volume 1 consists of a piezoelectric accelerometer 2 and a amplification and conversion circuit including an amplifier 3, a band-pass filter 4 of the recorder 5, and analog or digital spectrum analyzers 6.

To measure high-frequency pressure oscillations in a given volume, the vibroaccelerometer is mounted on an elastic element — a membrane made in one piece with the wall or fixed in the aperture of the volume wall. The dimensions of the membrane are chosen so that, taking into account the attached mass of the accelerometer, it has a natural frequency of 2, 7 times lower than the smallest measured frequency of pressure fluctuations, for example, when measuring in the frequency range 4-16 kHz, have a natural frequency of the membrane with a vibration sensor of about 1 5 kHz.

When exposed to measured pressure fluctuations, the membrane oscillates, equivalent to strong vibrations, which are measured by an information-measuring system with a high-frequency vibration accelerometer.

The dependence of the amplitude of pressure fluctuations is determined by the expression

DM.M§ „.,„ (,)

m

(.-- iSDe A (a)) P (a))

- C / fc

i); „p%

the amplitude of the oscillation of the membrane at a frequency f u) / - 27i; amplitude of pressure oscillations at frequency f a) / 2ji; membrane area; membrane stiffness;

Wfpes

- the frequency of natural oscillations of the membrane with an accelerometer;

- damping factor of the natural oscillations of the membrane. FIG. 2, this dependence is represented by curve 7.

 Since the signal of the vibroaccelerometer U (ui) is proportional to the second derivative of the amplitude of oscillation of the membrane, it is possible to record

U (u)) AMH uj4 (cJ). (2) From expressions (I) and (2), a formula is derived for the connection of an accelerometer signal with an amplitude of pressure oscillations

 and fez

Since we chose o), then

about

so for mechanical

systems - 1, the expression (C) is simplified to

u (u)) i f): §.

m

i

from where

roystva

P (u3) U (oJ) 5 --- “---,

those. The amplitude of the measured pressure fluctuations is proportional to the amplitude of the measured vibration accelerations with a constant coefficient in the operating frequency range.

FIG. 2, this dependence is represented by curve 8.

The nature of the curve shows that outside the resonance peak, caused by the natural frequency of the system, the membrane is an accelerometer, the frequency response of the device is linear.

The systematic error of the installation is:

one

wow

- will be on

one

50

the error level of the piezoelectric pressure gauges (10-15%) provided that the frequency of natural oscillations of the system membrane - accelerometer is 2.7-3.4 times less than the lower limit of the monitored frequency range

The region of significant distortion in the region of the resonant frequency of the membrane can be easily cut off by a band-pass filter 4, which has a cut-off frequency in the region of l, 5-l, 8f (curve 10 at 55 of Fig. 2).

As can be seen from FIG. 2 (curve 9), the frequency response of the entire system, which is the product of the frequency response of the resonant system — curve 8 at the frequency response of the band pass – curve 10, will be uniform in the frequency range and) 1, 8a3.

ej, Stiffness and mass of the membrane (resonator) are chosen so that at the maximum amplitude of the measured pressure fluctuations, the amplitude of the vibration accelerations is 5000 - lOOOOg. If the rigidity of the membrane is difficult to pick up, a thin-walled glass may be used instead, on the bottom of which an accelerometer nibro sensor is attached on the outside.

hp) iu (cj)

072564

Claims (1)

 Invention Formula A device for measuring high-frequency pressure oscillations, containing a membrane associated with a transducer for moving a membrane into an electrical signal, connected to a transducer, and a recorder, characterized in that, in order to expand the frequency range of measurements, it is equipped with an electric band-pass filter included between the output of the amplifier and the input of the recorder, and the transducer of the movement of the membrane into an electrical signal is made in the form of an accelerometer fO 15 Editor T. Parfenova Compiled by N, Bogdanova Tehred V. Kadar Order 1621/39 Draw 777 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab, 4/5 Production and printing company, Uzhgorod, st. Project, 4 Proofreader M. Demchik Subscription