SU934260A1 - Pressure pick-up with frequency output - Google Patents

Description

I

The invention relates to instrumentation engineering, in particular to pressure sensors with a frequency output signal.

A pressure sensor with a frequency output is known, comprising a cylinder-shaped resonator, excitation and removal electromagnets, a housing, magnets for adjusting the initial vibration frequency, and other elements. The measured pressure is supplied to the hermetic cavity formed by the resonator and the housing, depending on the pressure value, the stiffness of the resonator is measured, which leads to a change in the frequency of the mechanical resonance of the resonator tO.

The closest to the invention in its technical essence is a toroidal resonator pressure sensor for air shock waves, made in the form of a microwave resonator with external excitation and a manometric element in the form of a central resonator rod.

Under the action of the measured pressure, the capacitive gap between the end face of the gauge element and the end face of the second, stationary rod of the resonator changes, thus changing the resonant wavelength of the resonator 21.

ten

A disadvantage of the known device is the non-linear dependence of the resonant frequency on the measured pressure due to the use of the capacitance between the ends of the rods as an informative parameter.

e boz

WITH

(one)

SL

M

where S is the area of the end face of the resonator rod-,

ff is the gap between the ends; C - the capacity between the ends. 393 In an effort to increase the sensitivity and range of measured pressures, the nonlinearity of the dependence of the output signal on the input pressure sharply increases. The purpose of the invention is to improve the accuracy of conversion in a wide range of measured pressures. This goal is achieved by the fact that in the device the gauge element is made in the form of a bellows, and the movable electrode of the centered capacity of the resonator is made in the form of a cylindrical cap and mounted on the end of the bellows. The drawing shows the proposed. The device, a general view. The device comprises a housing 1 with a central rod 2, a bellows manometric element 3 with a cylindrical cap, frequency control element 5, communication elements 6, oscillating element 7, warming the resonator 8. Elements 1-6 form a super high-frequency resonator with a coaxial-rotor capacitive gap varying under the action of the measured pressure. The change in X of the coaxial capacitive gap (f is defined by the expression X f, (2) K K where I | ja "A PO, respectively, measured and reference pressure; K is the stiffness coefficient of the gauge element along the axial line. By appropriate choice of K. X in change of resonant frequency

g - x-:

to,

Substituted (2) in (3),

 v «| The CV, in turn, depends on the amount of overlap “L depends on the capacity of the coaxial gap

(5) In.

W

where GO is the speed of propagation of electromagnetic waves in a vacuum;

Claims (1)

Kj is the retardation factor. Obviously, with an appropriate choice of the ratio of the sizes of the sizes in the resonator, it is provided close to the linearization of SL in the form (L cLr + x, (6) (/ Q - the overlap value at the initial value of the measured pressure Р Е,, dР о - OQ ТГ- putting (7) in (5), we get 2L € e „k. |) the capacity of the resonator has two salting С С (+ CT-, - the capacitance between (10) С T. the ends of the rods ST Г the area of the butt (11) is equal that, J1 3ie € od 4Д d Ch 4 P (Low) the resonant frequency of the coaxial oscillator can be determined by the definition of In -t - inductive (14) L of the coaxial resonator. The tensions (8), and (I) in the expression (13). and the presets are obtained for vacuum air filling of the cavity of the dependence depending on the ratio fpej or Pj, where Pp is the reference pressure in the cavity of the resonator. Using the bellows as the rod of the coaxial resonator It also reduces the size of the sensor when operating at relatively low frequencies in the microwave range. This is due to the fact that the surface of the bellows simultaneously serves as a slow-down system for the microwave resonator which reduces the resonant frequencies of the oscillating microwave systems Wie reducing the propagation velocity of waves in the resonator. The quality factor of the resonators with a slow-wave system reaches a value of 10 or higher, which creates the prerequisites for excitation using a suitable active microwave oscillation device with a very low frequency overrun (10––. The nonlinearity of the conversion of pressure to the microwave frequency is almost zero, while ensuring a size ratio in accordance with the expression, 4o-f-I- The element of the excitation of microwave oscillations is combined with the design of the resonator in such a way that it will provide self-oscillations of the microwave in the system of the microwave resonator - the element of excitation of the microwave oscillations. Thus, the proposed device allows for linear pressure-to-microwave frequency conversion with a sufficiently high sensitivity. The presence of a deceleration system in the form of a bellows makes it possible to reduce the overall dimensions of the device when operating in the low-frequency portion of the microwave range. accuracy in a wide range in radio telemetry for the direct transmission of information about the pressure in the microwave range, as a primary converter of digital measurements pressure gauges, etc. DETAILED INFORMATION Sensor with frequency output, made of 8 kind of coaxial resonator with a concentrated capacitance and comprising a housing, a manometric sensitive element with a moving electrode, tuning, excitation and pickup elements, characterized in that in order to increase the accuracy of conversion in a wide range of pressure, in it the manometric element is designed as a bellows, and the movable electrode of the concentrated capacity of the resonator is made in the form of a cylindrical cap and fixed en at the end of the bellows. Sources of information taken into account during the examination 1. USSR author's certificate No. 304466, cl. G 01 L 11/00, I960. 2, Vardan nV, R. Toroidal resonator pressure sensor air shock waves. - Instruments and control systems, 1973f N 11, p. 41-42 (prototype).