RU199339U1 - Frequency pressure sensor - Google Patents

Abstract

The frequency pressure sensor claimed as a useful model relates to measuring equipment and can be used to measure the pressure of gaseous media, in particular, in air signal systems of aircraft or in pressure measurement systems with increased accuracy. The technical result is to compensate for the influence of the density of the measured medium on the oscillations of the sensitive element frequency pressure sensor The essence of the utility model lies in the fact that the frequency pressure sensor contains a pressure module including a vibrating sensing element, a signal processing and output circuit, a read-only memory, a circuit for excitation and registration of oscillations, which, in turn, contains: a signal receiver resonant circuit, amplifier, inverter, temperature sensitive element and temperature error compensation circuit, compensation circuit for changes in the density of the medium. The structure of the compensation circuit for changes in the density of the medium includes: a vibrating sensing element connected to a circuit for exciting and recording oscillations, a signal processing and output circuit that is connected to a temperature sensitive element, a temperature error compensation circuit and a circuit for exciting and recording oscillations. that the errors in measuring the pressure of media with different densities have decreased by an amount reaching about 30-40%. The declared frequency pressure sensor allows you to achieve a pressure measurement error of the order of 0.01% when measuring gases of different densities.

Description

The utility model relates to measuring technology and can be used to measure the pressure of gaseous media, in particular, in air signal systems of aircraft or in pressure measurement systems with increased accuracy.

Known frequency pressure sensors with a sensitive element in the form of a vibrating cylinder (see Gorenstein IA "Hydrostatic frequency sensors of primary information", Vulvet J. "Sensors in digital systems", Ageikin DI, Kostina EI, Kuznetsova NN "Control and regulation sensors"), the principle of operation of which is to create feedback and maintain the oscillations of the sensitive element at a certain harmonic of natural oscillations. The natural frequency of the sensing element depends on the measured pressure.

The indicated pressure sensors have an additional measurement error due to the influence of temperature on the sensitive element and the influence of the density of the measured medium (for example, air, nitrogen, etc.) on the vibration of the sensitive element. One of the ways to reduce the indicated additional measurement error is to use an additional element in the frequency pressure sensor that is sensitive to temperature or to the density of the measured medium, followed by compensation of the output signal according to information from the additional element, for example, utility model No. 123 143 "Frequency pressure sensor" and utility model No. 159 820 "Frequency pressure sensor".

For the prototype, a useful model No. 159820 "Frequency pressure sensor" was selected, including a pre-transducer, a vibrating sensing element (vibrating cylinder), a circuit for exciting and maintaining vibrations, a signal processing and output circuit, a read-only memory (ROM) for storing calibration coefficients, temperature-sensitive element, compensation circuit for temperature error and compensation circuit for changes in the density of the medium.

The disadvantage is that the issue of the influence of temperature on the error in measuring the density of the medium has not been resolved, which does not fully compensate for the effect of the density of the medium on the pressure measurement.

Preliminary results showed that the contribution of the temperature error to the compensation signal can reach 50%, primarily due to the ambiguous dependence of the output signal on density on temperature.

The problem to be solved by the claimed utility model is to reduce the error in measuring the pressure of media with different densities.

The technical result consists in compensating the influence of the density of the measured medium on the oscillations of the sensitive element of the frequency pressure sensor.

The specified technical result is achieved by the fact that a density change compensation circuit is introduced into the design of the frequency pressure sensor, which is similar in design to the pressure module, which makes it possible to separately perform temperature compensation for pressure measurement and density measurement.

The frequency pressure sensor contains a pressure module and a density change compensation circuit. The pressure module includes a vibrating sensing element, a signal processing and output circuit, a read-only memory, a vibration excitation and recording circuit, a temperature sensing element, and a temperature error compensation circuit. The circuit for exciting and registering oscillations, in turn, consists of a resonant circuit signal receiver, an amplifier, and an inverse converter.

A vibrating sensing element, a circuit for excitation and registration of oscillations, a circuit for processing and issuing a signal, a temperature-sensitive element and a compensation circuit for a temperature error are included in the compensation circuit for changes in the density of the medium.

FIG. 1 shows a block diagram of the proposed frequency pressure sensor, where:

1 - vibrating sensing element (vibrating cylinder);

2 - receiver of resonant circuit signals;

3 - amplifier;

4 - reverse converter;

5 is a diagram of signal processing and output;

6 - read only memory (ROM) for storing calibration coefficients;

7 is a diagram of excitation and registration of oscillations, including (2), (3), (4);

8 - pressure module, including (1), (5), (6), (7);

9 - thermosensitive element;

10 - circuit for compensation of temperature error;

11 - scheme for compensating for changes in the density of the medium, including:

1 '- vibrating sensing element (vibrating cylinder);

2 '- receiver of resonant circuit signals;

3 '- amplifier;

4 '- inverter;

5 '- signal processing and output circuit;

7 '- circuit for excitation and registration of oscillations, including (2'), (3 '), (4');

9 '- thermosensitive element;

10 '- compensation circuit for temperature error;

11 '- temperature error compensation circuit.

The principle of operation of the proposed frequency pressure sensor is as follows: the excitation circuit and registration of vibrations 7, by creating a positive feedback, maintains the vibrations of the vibrating cylinder 1 in resonance at a certain harmonic, and the frequency of the natural vibrations of the vibrating cylinder depends on the measured ambient pressure, which is supplied to the internal cavity of the sensing element: an increase in the measured pressure leads to a change in the geometric dimensions and rigidity of the sensing element, the frequency of natural oscillations also increases, and due to the positive feedback, the excitation circuit and registration of oscillations 7 changes the frequency of excitation through the inverse transducer 4 to obtain the maximum amplitude of oscillations of the walls of the vibrating cylinder in accordance with the resonance curve.

The calibration coefficients stored in the ROM 6 are used to form the output signal of the frequency pressure sensor to match the output signal to the measured pressure, taking into account the nonlinearity of the sensor conversion function and the dependence of the measured pressure on temperature.

The temperature error compensation circuit 10 converts the output signal from the temperature sensitive element 9 into an electrical signal, taking into account the nonlinearity of the output signal of the temperature sensitive element and the nonlinearity of the change in the natural frequency of the sensitive element from the measured pressure and temperature. The location of the thermosensitive element is determined by the requirements for the dynamic characteristics of the pressure sensor; when placed in close proximity to the sensitive element, a minimum temperature dynamic error can be achieved.

In essence, elements 1 ', 5', 7 '(with inputs 2', 3 ', 4'), 9 ', 10' are similar to elements 1, 5, 7 (with inputs 2, 3, 4), 9, 10 The difference is that the environment, the pressure of which is to be measured, is supplied simultaneously to the inner and outer cavities of the sensing element. Thus, the added mass influences the vibrations of the walls of the sensing element, and the vibration frequency of the walls depends on the density of the measured medium.

The principle of operation of circuit 11 is similar to the previously described principle of operation of the pressure module 8 of the frequency pressure sensor. In the circuit for processing and issuing a signal 6, compensation occurs in the output signal of the density of the measured medium, taking into account the temperature error in the compensation circuit for changes in density.

Experimental studies of the frequency pressure sensor showed that the errors in measuring the pressure of media with different densities decreased by an amount reaching about 30-40%.

In general, the proposed technical solution makes it possible to achieve a pressure measurement error of the order of 0.01% when measuring gases of various densities.

Claims (1)

A frequency pressure sensor containing a pressure module including a vibrating sensing element, a signal processing and output circuit, a read-only memory, a circuit for excitation and registration of oscillations, which, in turn, contains a resonant circuit signal receiver, an amplifier, an inverse transducer, a temperature-sensitive element and a circuit compensation of temperature error, a compensation circuit for changes in the density of the medium, characterized in that the composition of the compensation circuit for changes in the density of the medium includes: a vibrating sensing element connected to a circuit for excitation and registration of oscillations, a circuit for processing and issuing a signal that is connected to a temperature sensing element, a temperature compensation circuit errors and circuit of excitation and registration of oscillations.

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