SU717582A1 - Frequency-output absolute pressure sensor - Google Patents

Description

(54) ABSOLUTE PRESSURE SENSOR WITH FREQUENCY. OUTLET

which leads to an increase in the cost of the sensor.

The purpose of the invention is to increase the sensitivity of converting the Pressure measured by the sensor to the frequency while reducing the cost of its production.

This goal is achieved due to the fact that in the sensor containing a thin-walled cylindrical resonator, on both: the other side are fixed gas-tight screens, as well as elements of oscillation excitation systems, and one of the gas-tight screens is made in the form of elastic, and the other rigid coaxial cylinders, moreover, the cross section of one of the screens is shaped in such a way that it forms with opposite screen (circular initial section) contact lines that coincide with the nodal meridians and resonator. Due to this, mechanical contact / of both cylinders with a resonator along the nodal meridians is ensured. With such a sensor design, in cross section perpendicular to the cavity axis, unlike the known construction, a smooth change in the gap between the resonator surfaces and facing the screen surfaces is achieved. to a sinusoidal (from the zero gap near the nodal-meridian to the maximum. in the middle between two adjacent nodal meridians) It is due to this gap profile and both the maximum slope of the conversion characteristic and the maximum suppression of possible side resonances are provided at the same time.

Valid. Two equivalent structural schemes for constructing the proposed sensor: one — when the rigid cylinder is located inside the resonator and elastic outside, and the other — when the elastic cylinder is located inside the resonator, and the rigid cylinder outside.

Figure 1 shows a General view of a variant of the design of the sensor, in which the rigid cylinder is located inside the resonator and has a circular cross-section; figure 2 is a General view of a variant of the design with the same arrangement of a rigid cylinder, however, having a cross-section of a pillow shape; Fig. 3 is a general view of a variant of the design, Ta KotopoM rigid C; a circular cylinder section covers the resonator outside; in Fig. 4, a diagram of a self-excitation system of the sensor.

A variant of the design of the sensor (figure 1) is arranged as follows. The sensitive element assembly (ECA), which converts pressure from one meter to another, consists of three parts I of a rigid cylinder 1 made, for example, of ceramics and the base of an EChE, thin-walled cylindrical resonator 2, which is a thin-walled tube section constant section, having in the free state the shape of a regular circle, and an elastic cylinder 3, the cross section of which in the free state is close to a square with rounded corners, and the dimensions of this figure are For example, if we embed a circle into it, then the radius of this circle will be less than the radius of the circle described around the cross section of a rigid cylinder 1. If Pe denotes the perimeter of the cross section of the inner surface of the outer screen, Pr is the perimeter of the cross section of the outer surface of the resonator. Ave., the perimeter of the cross section of the inner surface of the resonator and, finally, A .; - the perimeter of the cross section of the outer surface of the inner screen, then the following approximate relations are maintained between the indicated quantities:

five-.

. (2)

The thicknesses h, hp and h, y of rigid cylinder 1, resonator 2 and elastic cylinder 3, respectively, should also satisfy approximate relations:

(3)

.

The sensing element assembly is enclosed in a protective housing consisting of a cylindrical casing 4 with flared 5, a transitional mounting sleeve 6 and a cover 7c with an opening 8 for connecting the choke (not shown in Fig. 1) through which the measured pressure is through holes in sleeve b is supplied to the ACCU. Electrodes 9 and 10 of capacitive resonant vibration excitation systems and output signal pickup are applied to the inner surface of a rigid ceramic cylinder 1.

The ECA is connected to the case parts of the Sensor using vacuum tight joints 11 and 12 (welding, soldering). A similar joint 13 connects the body parts 4, 6, and 7. With the help of the electrical leads 14, the sensor is included in the self-excitation system circuit, two versions of which (for external and internal cases. The positions of the rigid cylinder 1) are shown in FIG. four.

Claims (2)

Figure 2 shows another variant of the proposed sensor design, differing from the first one only in that the cross section of the rigid cylinder 1 has a shape close to the shape of a square with rounded corners, and the resonator 2 and the elastic cylinder 3 in a free state have a round settlement. V. -. Fig. 3 shows a variant of the design in which the rigid cylinder 1 pa is placed outside the resonator 2, and the thrust cylinder 3 is inside it. At this time, the rigid cylinder 1 plays the role of the protective casing of the device at the same time, due to which the overall quality of the sensor components is reduced. At both ends, the rigid cylinder 1 is closed by covers 15 and 7, and an opening 8 is made in the cover 7 for connecting a choke (which is not shown in the drawing). Both the rigid cylinder 1 and the resonator 2 in the free state have the shape of regular circles in cross section and are elastic in shape. cylinder 3 is a shape close to a square with rounded edges. In all the designs described here, capacitive excitation and removal systems are used, although in principle it is possible to use these systems of other types. Any of the above options for the sensor works as follows. From the terminals from the pickup electrodes 9, the signal is fed to the input of the electronic unit of the self-excitation system (EBS) 17 and then to the terminals connected to the electrodes 10 of the oscillation system of the resonator 2. Together with the resonator 2, the electrodes 9 and 10 and the block 16 form an electromechanical self-oscillatory system, oscillation frequency which is close to the natural frequency of bending oscillations of the resonator. With a change in the measured pressure and, consequently, the elasticity of the gas in the gaps between the resonator 2 and the cylinders 1 and 3, the natural frequency of the bending oscillations of the resonator also changes. The use of the described sensor ensures the achievement of the limiting steepness of the characteristic potentially possible for sensors of this type, and reducing the cost of manufacturing such sensors. An invention of an absolute pressure sensor with a frequency output, comprising a cylindrical resonator, gas-tight screens located on both sides of the resonator, and an excitation and pickup system, characterized in that, in order to increase the sensitivity, one screen is designed as elastic and the other rigid cylinders arranged coaxially, with the surfaces of the screens and the resonator contacting along the pin of the nodal meridians of the resonator. Sources of information taken into account in the examination 1. The author's certificate of the USSR №181848. cl. G 01 L 11/00, 1965. 2. USSR author's certificate for application number 2598873 / 18-10, cl. G 01 L 11/00, 03/30/78 (prototype). h: ""with ri I I -I "" - - J N e4j t5 t-Q iS T 9 2} in sixteen