SU1765737A2 - Method for metering pressure pulse gauge - Google Patents

Description

one

(61) 1182296 (21) 4783505/10 (22) 1/16.90 (46) 30.09.92. Bul №36

(71) Research Institute for Physical Measurements

(72) S.D.Zabrodina and T.N.Politmentseva

(56) 1. Levshina E.S. and Novitsky P.V., Electrical Measurements of Physical Values. L .: Energoatomizdat, 1983.

2. USSR author's certificate No. 1182296, cl. G 01 L 27/00, 1977. (54) METHOD FOR CALIBRATING PULSAY PRESSURE SENSORS

(57) Use: in metrology and measurement technology. The essence of the invention:

Before calibration, the sensor output parameters are measured under normal conditions and when exposed to temperature and pressure. The block diagram includes a sensor and parallel to it a circuit and resistances and capacitances, the values of which correspond to those measured taking into account the output parameters of the sensor in normal conditions. The shock wave acts on a calibrated sensor installed in the pipe end wall. The output electrical signal is corrected by the circuit to a value corresponding to the operating conditions, then amplified, differentiated by a link, and stored in the memory of the digital recorder. 1 il.

The invention relates to metrology and measurement technology, in particular, to methods for calibrating piezoelectric pressure pulsation sensors, and is an improvement of the known method described in the author. No. 1182296.

The known method of calibration of pressure sensors 1 involves forming a step function of pressure at the sensor input, converting the input action into an electrical output signal, differentiating it over time, converting it into a digital code, storing and calculating the amplitude-frequency characteristic (AFC) of the sensor.

The disadvantage of the method is the limited ranges of temperature and pressure level generated at the sensor input, which leads to the conversion of the input action into the output signal under the conditions

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WITH

different from the workers, and thereby reduces the reliability of the output signal.

The aim of the invention is to increase the reliability of the determination of the amplitude-frequency characteristic.

The goal is achieved by the fact that in the method of calibration of pressure pulsation sensors in 2, including the formation of a step function of pressure at the sensor input, converting the input action into an output electrical signal, differentiating it over time, converting it into a digital code, storing and calculating the frequency response of the sensor in a climatic chamber in which pressure and temperature are created, corresponding to the operating condition, the insulation resistance and the sensor capacitance are measured, then connected in parallel Exit sensor resistance R and capacitance C values which are selected by the ratio m:

J

About SP 4

from 1

Yu

R

Rh

RH - Rp

(1) and С Cp - Сн, (2)

where Rp is the insulation resistance of the sensor, measured at pressure and temperature, corresponding to the operating conditions;

RH is the insulation resistance of the sensor under normal conditions;

Ср - sensor capacity, measured at pressure and temperature, corresponding to the operating conditions;

The capacitance of the sensor is under normal conditions.

The essence of the invention is as follows. The frequency response of the sensor depends on the working conditions, i.e. on temperature and pressure level generated at the sensor inlet. During calibration, these conditions are simulated by adjusting the output parameters (RM3 and Cd) of the sensor.

Measurement of the frequency response of the piezoelectric sensors under conditions corresponding to the working environment (temperature of the working medium from minus 196 to plus 700 ° С, pressure - up to 2000 kgf / cm) is not possible because the field of application of calibration equipment is limited in temperature ( in the case of installation on a liquid medium) and pressure (in the case of work on a gaseous medium).

It is known that the non-uniformity of the frequency response of the sensor in the low-frequency region significantly depends on the value of the insulation resistance and the capacitance of the sensor and can be determined by calculation (for the use of a voltage amplifier in the measuring circuit).

However, a comparative analysis of the calculated and experimental data showed. that the formula is approximate and the discrepancy between the results of the experiment and the calculated ones is no less than two times.

The drawing shows an example of a block diagram of an installation that implements the proposed method of calibration, which shows the high-pressure chamber 1, the membrane assembly 2 and the working channel 3 of the shock tube, the graduated sensor 4; contour 5 of resistance R and capacitance MF, amplifier 6, differentiating element 7, digital recorder 8, frequency analyzer 9, plotter 10.

The method is carried out as follows.

Before calibration, the output parameters of the RH and Cn sensors are measured under normal conditions and with simultaneous exposure to temperature and pressure of Rp and Cp, for which the sensor is set

in a thermostat (or cryostat), which is connected via a separation chamber with a piston-type manometer via a pipeline. The separation chamber has an additional air inlet and a filter made of a soft porous material (for example, felt) that does not allow oil to enter the working cavity of a thermostat (cryostat). When the required temperature and pressure levels are reached on the sensor membrane, Reese and Sd are measured.

After that, sensor 4 and parallel to it a contour 5 of resistance and whose values correspond to those measured with regard to the output parameters of the sensor in normal conditions are included in the block diagram.

A shock wave (pressure surge) generated in the working channel 3 of the shock tube acts on a graduated sensor installed in the end wall of the tube. The electrical signal from the output of the sensor is corrected by circuit 5 to a value corresponding to the operating conditions (i.e. under simultaneous exposure to temperature and pressure), then amplified by amplifier 6, differentiated by link 7 and stored in the memory of digital recorder 8. The recorded signal is output from digital the recorder cyclically. The frequency of the output signal is reduced (the frequency transport factor is set by the experimenter) for carrying out in accordance with the capabilities of the frequency analyzer 9.

The resulting analysis of the frequency response of the sensor is output to the plotter 10.

Introduction to the block diagram of the calibration parallel to the sensor circuit of the resistance and capacitance allows to simulate the working conditions when a pressure stage is formed at the sensor input and, thus, to increase the reliability of the output signal.

This eliminates the need to develop expensive equipment.

The technical and economic advantage of the method in comparison with the known method is that, in its implementation, the reliability of determining the frequency response of the sensors increases by more than 50%.

Claims (1)

Invention Formula The method of calibration of the pressure pulsation sensors according to the auth. No. 1182296, characterized in that, in order to increase the reliability of determining the amplitude-frequency characteristic, the sensor is preliminarily placed in the climate a chamber in which pressure and temperature are created in accordance with the operating conditions measure the insulation resistance and the sensor capacitance, then the resistance R and capacitance C are connected in parallel with the sensor output, the values of which are chosen according to the ratios R Rp RH RH Rp and C Wed - Sn, 0 where Rp is the insulation resistance of the sensor, measured at pressure and temperature, corresponding to the operating conditions; RH is the insulation resistance under normal conditions; Ср - sensor capacity, measured at pressure and temperature, corresponding to the operating conditions; SN is the capacitance of the sensor under normal conditions, Yu