SU1364929A1 - Pressure transducer - Google Patents

Abstract

The invention relates to the field of measurement technology. The purpose of the invention is to simplify the assembly and adjustment technology and to improve the measurement accuracy. The inclusion of pathogens 6 and receivers 7 according to this scheme provides the minimum pickup and the maximum signal-to-noise ratio at the output of the operational amplifier 16. In the output amplifier 17, the zener diodes 18 create the required nonlinearity such as saturation of the output characteristic of the output amplifier 17 when the latter operates in a linear mode. Resistors 20 form current feedback to increase the output impedance of the output amplifier 17. The self-excitation system provides self-excitation of a cylindrical resonator (CR) strictly at its own frequency. When a pressure difference appears, acting in the external and internal planes of the CR, the natural frequency of the CR and the frequency of self-oscillations in the self-excitation system, traces change, the frequency of the electrical output signal is an informative parameter. A special feature of the sensor design is the construction of a housing that allows for the necessary heat treatment of a fully enclosed CR. 3 il. SP

Description

fut.i

The invention relates to a measurement technique, in particular, pressure sensors with a frequency output.

The purpose of the invention is to simplify the assembly and adjustment technology and to improve the measurement accuracy.

FIG. 1 shows a pressure sensor, a slit; in fig. 2 - connection of exciters and receivers in the sensor self-excitation mode; in fig. 3 - split forms with different frequencies to, j and uj, where is the number of half-waves, is the number of waves.

The pressure sensor consists (Fig. 1) of body 1, made in the form of a flanged sheet, in which a welded cylindrical resonator 2 is fixed, while the bottom of the resonator is connected to the fixing protrusion 3 to reduce the effect of the fixing on its work. 1 having four windows 4 with a size of

/ with

circumferential direction 45, wearing a sleeve 5, in which four drivers 6 and four receivers 7 are installed in the radial holes. The drivers 6 and receivers 7 are made equally in the form of 8 electromagnetic capsules polarized by a permanent magnet and having magnetic arrays 9 with a tapered pole tip and the sleeve 10, the electric winding 1 1 and sealing thin non-magnetic disk 12 (for example, alloy 36NHT). Pathogens 6 are installed at an angle of 90 relative to each other. Receivers 7 are also installed accordingly. Each capsule is sealed to the lateral surface of sleeve 5, for which sleeve 5 has four flat faces with the required grooves necessary for welding (Fig. 1 ), or chamfers for soldering. The sleeve 5 is hermetically connected to the flange of the housing 1, and the end 13 of the sleeve 5 is tightly attached to the lid 13 with the fitting of the external cavity of the resonator, into which the medium passes through the holes 14. To the other side of the flange of the housing 1 is tightly attached to the cover 15 with the fitting of the internal cavity of the resonator.

FIG. 2 shows the connection of pathogens (B, - B) and receivers 7 (P - P). The inclusion of pathogens 6 and receivers 7 in accordance with the scheme (Fig. 2) ensures minimum pickups and maximum signal-to-noise ratio at the output of summing operational amplifier 16 (Y,). Amplifier 17 (Y) is an output amplifier in which zener diodes 18 (VD) and 19 (VD) create the required non-linearity such as saturation of the output characteristic of amplifier 17 when the amplifier itself operates in linear mode, and resistors 20 (Rg) and 21 (Rg) form current feedback to increase the output impedance of the amplifier 17. The self-excitation system shown in Fig. 2 provides a self-excitation of a cylindrical resonator strictly at a natural frequency corresponding to the form, where n is the number of waves in the circumferential direction (shown by a dotted line in Fig. 2); m is the number of half-waves in the longitudinal direction of the cylindrical resonator, which is caused by the minimal phase shift between the speed of movement of the resonator wall (electrical voltage at the receivers) and the driving force (electrical current in the exciters).

FIG. The dotted line in Fig. 3 shows the worst possible initial position of the pathogens 6 and the receivers 7 relate. H1 / 71

tions and “J ,, where is the number of half-waves, is the number of waves.

The required position of the pathogens 6 and receivers 7 is achieved by turning to +22.5, i.e. in the antinodes of the form with si-d, but you can get an identical result by turning in the antinodes of the form with il; (-22.5 °).

The pressure sensor operates as follows.

With the appearance of the pressure difference acting in the external and internal cavities of the resonator 2, the natural frequency of the resonator on the excited form, and thus the frequency of self-oscillations in the self-excitation system, hence the frequency of the electrical output signal and 5 (, | j, which is informative parameter (Fig. 2). In the self-wake-up system, the bending oscillations of the resonator with the help of receivers 7 (P – P included in a differential circuit are converted into two antiphase signals, C) (1multiple and amplified in Ithel x 16 and 17. The output signal, and d., converted

exciters 6 into excitatory forces distributed in the form of oscillations,.

The phase relations, the necessary amplification along the self-excitation system contour, and the saturation nonlinearity (zener diodes VD, VD) provide self-oscillations with frequency c / (and,) the chosen split oscillation shape.

A feature of the pressure sensor design is the implementation of the housing 1, which allows the necessary heat treatment of the cylindrical resonator 2 completely fixed in it. This determines the initial position of the split eigenmodes of the fixed resonator 2 arising from technological deviations relative to the housing (base).

FIG. 3 shows split

,(eleven

W

(five)

forms with different frequencies w and where and.

In addition, the attachment of the bottom of the resonator 2 to the fastening protrusion 3, having a diameter d, which is substantially smaller than the diameter of the resonator 2d (p) ensures the vibration resistance of long cylindrical resonators with

the minimal effect of the conditions of fixing the leu on the operation of the resonator increases accuracy.

After installation of the capsules and their fastening, the sleeve 5 makes it possible to adjust the position of the pathogens and receivers with respect to the housing strictly according to the antinodes of oscillations of a split shape. In FIG. 3 this is indicated by arrows with respect to the split form with the frequency s -,.

This adjustment provides the largest possible range of measurements. This is due to the fact that, due to the inevitable technological deaths of a cylindrical resonator, under the action of pressure, perishes begin

change resulting in a turn

split forms of the resonator relative to pathogens and receivers. The maximum range of measured pressures is limited by an abrupt change in the frequency of self-oscillations associated with the transition of resonator oscillations from one split form to another, which is caused by their rotation relative to pathogens.

. Yu

i15 - 20

,

5 b, 30

35 40

g

gQ

55

and receivers, i.e. transition of self-oscillations from frequency and, to frequency and. The proposed installation of the same exciters and receivers in each antinode of oscillations of a cylindrical resonator at the shape of oscillations, and the choice of dimensions of the resonator, ensuring the minimum frequency of its natural oscillations, ensures that self-oscillations in the self-excitation system cannot switch to higher forms at any pressure change (pressure differential) until destroyed. resonator. However, this leads to a cylindrical resonator of relatively long length, the bottom of which must be fixed for vibration resistance.

Symmetrical installation of the capsules in the magnetic core sleeve 5, their implementation with tapered pole pieces and their inclusion in accordance with the scheme (Fig. 2) significantly increase the signal / noise ratio, which increases the measurement accuracy, and sealing the capsules with nonmagnetic metal discs 12 provides evacuating the external and internal cavities of the resonator 2.

Claims (1)

Invention Formula A pressure sensor comprising a housing, two covers with inlet nipples, a cylindrical resonator with a deaf bottom and an installation tray fixed in the housing, and excitation and vibration pickup systems made in the form of polarized electromagnets with a cylindrical shell forming a pole tip in the form of a truncated a cone, characterized in that, in order to simplify the assembly and adjustment technology and to increase the measurement accuracy, in it the body is designed as a cup with a flange and a sleeve with openings located outside it, in which Electromagnets, which are led out into the internal cavity of the case by pole tips through windows made in the glass wall, are fixed, each pole tip is sealed at the end with a non-disk, and in the bottom of the glass there is a protrusion to which a depth is attached. 1364929 This is the bottom of the resonator; moreover, a “cup” of the cup is placed, and a cap with a choke is attached to the end of the cup to the B-IVJIKH.