SU427256A1 - PRESSURE SENSOR WITH FREQUENCY OUTPUT SIGNAL12 - Google Patents

Description

The invention relates to the field of instrumentation technology, in particular, to vibration-frequency sensors for measuring the pressure of gaseous and liquid media.

In the known pressure sensors containing a cylindrical resonator, an electromagnetic excitation system is used, which significantly limits the use of ferromagnetic materials for the fabrication of resonators, since such iKaiK quartz, beryllium bronze, widely used for the manufacture of elastic sensing elements, is unsuitable.

In the proposed sensor, in order to simplify the design, as well as to ensure the possibility of using resonators from both ferromagnetic and non-magnetic materials, the permanent magnets, in a multiple of two, are arranged around the resonator so that they form a quadrupole magnetic field, between the poles of which there are electrodes of the capacitive removal system, and the ends of the resonator are connected to an alternating current source.

FIG. 1 shows the sensor section; in fig. 2 is a circuit diagram of the excitation system; in fig. 3-8 - section aa to f. 1 with possible embodiments of a magnetic circuit providing a quadrupole magnetic field around the resonator.

The sensor includes a cylindrical body / of magitite of a flexible material, in which 5 permanent magnets 2 are pressed in, in a multiple of two, located around the resonator 3, made in the form of a cylindrical thin-walled tube, from one end - which is fixed to the tail and to the 4th of the original 5, and on the other hand, a plug in with a deaf hole intended for soldering the leads 7 for including the resonator 3 into the circuit of the excitation system, and the insulator S, which prevents the occurrence of longitudinal voltages in the resonator when its length s with the temperature change. The second end of the housing 1 is closed by fitting 9. The housing} is connected to fittings 5 and 9 tightly. Around the resonator 3 there are placed electrodes 10 of a capacitive excitation system, which form capacitors connected to each other by the outer cylindrical surface of the resonator, pairwise parallel to and connected: 1; through the resistors TI and G2 to the DC source 12. In some embodiments of the magnetic circuit, magnetic flux concentrators 13 are inserted from Q prepared from small soft materials with high saturation induction. ,: ./,.:,: I | : (f .. 3 inf: r, .j 1 "r-Wa.. j The sensor works as follows. The measured pressure through the nozzle 5 is fed into the internal cavity of the resonator 3, which together with the capacitive excitation system forms an electromechanical auto-oscillatory system whose oscillation frequency is equal to the natural oscillation frequency of the resonator 3. The excitation system maintains continuous damping oscillations of the resonator 3. When the resonator oscillates, U 3, the capacitors formed by the electrodes 10 and the outer cylindrical surface resonate 3. As a consequence, the input {amplifier 12 sho is an alternating voltage of the same frequency, 5 as the oscillation frequency of the resonator, which is fed to the resonator 3. When an alternating current flows through the resonator, it is influenced by the forces that ensure its further buildup. the signal of amplifier 12 is simultaneously the output signal of the sensor. 20 4 the phase characteristic of amplifier 12 is chosen so that self-excitation conditions are fulfilled in the working frequency range. Due to this, continuous oscillations are maintained in the system, the frequency of which is one-way associated with the measured pressure. The subject of the invention is a pressure output sensor with a frequency output signal, containing a pressure sensitive cylindrical resonator and permanent magnets, characterized in that, in order to simplify the construction, as well as to enable the use of resonators from both ferromagnetic and non magnetic materials, therein the magnets, 8 times a multiple of two, are located around the resonator so that they form a quadrupole magnetic field, between the poles of which there are electrodes of the capacitive removal system, and “about a resonator and connected to AC power.

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