SU964503A1 - Pressure difference sensor with frequency output signal - Google Patents

Description

(54) PRESSURE DIFFERENCE SENSOR WITH FREQUENCY OUTPUT

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The invention relates to measuring instrumentation, in particular, to devices for measuring the pressure difference between liquid and gaseous media.

A pressure sensor with a frequency output signal is known, comprising a housing that is sensitive to a pressure thin-walled cylindrical ferromagnetic resonator with hermetically mounted spring loaded bellows, the inner cavities of the bellows communicating with the internal cavity of the resonator and filled with gas, excitation and removal of oscillations of the resonator 1.

The disadvantage of this sensor is low measurement accuracy due to a decrease in the quality factor of its oscillating system, due to the dissipation of the oscillation energy at the points of attachment of the resonator due to the remoteness of these places from the oscillation nodes of the resonator.

Closest to the invention in its technical essence is a sensor for varying the pressure difference, comprising a housing in which a cavity in the form of a hollow chamber is mounted.

a tone filled with two immiscible liquids, bellows installed on the tuning fork, the excitation and pickup system, and a recording device 2.

A disadvantage of the known device is the low measurement accuracy due to the substantially nonlinear conversion characteristic, which makes it difficult to process the output frequency signal. In addition, the sensitivity to the measured pressure is determined, in addition to the geometrical parameters of the oscillatory system, by the difference in the densities of the liquids filling the tuning fork.

The purpose of the invention is to improve accuracy by measuring 15 by linearizing the characteristics and increasing sensitivity.

Claims (1)

The goal is achieved by the fact that in the pressure sensor with a frequency output signal, comprising a housing in which a resonator is installed, in the form of a hollow tuning fork, a bellows installed at one end of the tuning fork, a system for excitation and vibration pickup, and a recording device, a second one is inserted. 39 identical to the first, a tuning fork with bellows and a system of excitation and vibration pickup, connected to the first common channel, located diametrically opposite to the bellows, in this case each tuning fork is half filled with liquid. The drawing shows the proposed device. The pressure sensor comprises a housing 1 in which two, for example double, KaAiegTOHa 2 and 3, are installed vertically, in parallel and symmetrically, the internal cavities of which are connected by a common channel 4. The common channel and adjacent branches of tuning forks 2 and 3 are half filled with liquid 5. The forks 2 and 3 communicate with bellows 6 and 7 installed in sealed compartments 8 and 9 of housing 1, equipped with fittings 10 and 11 for supplying measured pressures. To equalize the pressure of the gas in the bellows - bi 7 and tunnel forks 2 and 3, a valve 12 is provided, and for ease of disassembly, the sensor is equipped with flanges 13 and 14. To excite oscillations of the forks 2 and 3, electrons magnets L5 and 16 are provided, and for removal - electromagnet adapters 17 and 18 (when making tuning forks, for example, of quartz glass, magnetic labels are mounted on branches x against excitation and receiver), included in the circuit of amplifiers 19 and 20 according to the autographic scheme. The outputs of the amplifiers 19 and 20 are connected to the input of a mixer 21, the output of which is connected via a low-frequency filter 22 to a measuring device 23. The device operates as follows. At equal pressures Pj and Pj in compartments 8 and 9, the bellows 6 and 7 are practically uncompressed, and liquid 5 fills the branches of the cometons 2 and 3 up to half of their lengths. - Tuning forks 2 and 3 are driven by feedback circuits 17, 19, 15 and 18, 20, 16 at equal resonant frequencies. The difference frequency at the output of the mixer 21 is zero and the needle 23 is at zero in the center of the scale. As the pressure in chamber 9 increases, so that P, Pr, bellows 6 expands and the background 7 forces are compressed by transferring pressure through the gas-liquid system, as a result, the level of liquid 5 in tuning fork 2 decreases, and in tuning fork 3 it increases, and their frequencies vary accordingly. The difference frequency is set in mixer 21 and, after the low-frequency signal is detected, the indicator 22 in the filter 22 causes a deflection of the gauge 23 arrow. Provided that P2 PI, the level of liquid 5 decreases in tuning fork 3 and increases in tuning fork 2, the resonant frequency of fork 3 increases as a result and the tuning fork 2 decreases, as a result of which the difference frequency at the output of the mixer 21 changes sign and the measuring device arrow is deflected in the other direction. Thus, the invention reduces the linearity error, resulting in improved measurement accuracy. In addition, by increasing the difference between the densities of the liquid and the gas, the sensitivity of the device is increased. The invention The differential pressure sensor with a frequency output signal, comprising a housing in which a resonator in the form of a hollow tuning fork is installed, a slope mounted on one end of the tuning fork, an excitation and pickup system, and a recording device that differs from by linearizing the characteristics and increasing the sensitivity, a second, identical to the first, tuning fork with bellows and an excitation and pickup system, introduced to the first common channel, is inserted into it diametrically opposed to the bellows, with each tuning fork half filled with liquid. Sources of information taken into account during the examination 1. USSR author's certificate No. 658416, cl. G 01 L 11/00, 07.12.77.2. USSR author's certificate in application N 2788858 / 18-10, cl. G 01 L 9/00, 07.06.79 (prototype).