SU871001A2 - Pressure pickup - Google Patents

Description

(54) PRESSURE SENSOR

I

This invention relates to a measurement technique.

According to the main author. St. No. 759876, a pressure sensor is known, comprising an elastic element in the form of a membrane with a rigid center and a shoulder at the periphery attached to the sensor body, and a stop mounted with a gap relative to the rigid center. On the membrane are two measuring circuits. One circuit, consisting of strain gauges located at the boundaries of the rigid center and the collar, performs measurements at low pressures until the membrane touches the abutment. The second additional strainer circuit contains strain gauges located at a distance of 0 from the border of the shoulder and the hard center, where (3 is the distance between the shoulder and the hard center. The additional strain gauge allows measurements in the extended pressure range, including pressure

nor, in which the stop restricts the movement of the rigid center.

Insufficient accuracy of the pressure sensor due to the presence of the nonlinearity of the calibration chaoacteristics of the additional circuit and the difficulty of its linearization during tuning.

The aim of the invention is to improve the measurement accuracy by reducing the non-linearity of the calibration characteristic.

The goal is achieved

15 by the fact that in the proposed pressure sensor, one of the additional strain gauges is made of a composite of two radially oriented teresistors located

Claims (2)

K on the flexible part of the membrane. One of the bottom; located at the border with a hard center, / and the other at the border with burtikKOM; 3 1 shows a membrane yes. FIG. pressure gauge, general view, in FIG. 2 membrane sensing element. The pressure sensor contains an emphasis 1 and a membrane sensing element. 2. Membrane sensitive element 2 has a rigid center 3 and a flange 4, at the borders of which on the flexible part of the membrane is the main bridge strain circuit formed by strain gages 5-8. Equally oriented strain gauges lying near the boundaries of the hard center 3 and collar 4, 1) are located in the adjacent arms of the bridge. Three strain gauges 9, 10, 11, an additional strain gauge circuit are located in the central region of the flexible part of the membrane, and one bridge arm is formed of series-connected and equally oriented strain gauges 12 and 13, one of which (12 is located at the boundary of the hard center 3, and the other (13 - at the border of the collar 4. The sensor works as follows. When a pressure of less than nominal is applied, the membrane is deformed, but does not touch the stop. At the same time, output signals proportional to pressure are supplied to the strainer circuit. At high pressures and the stop restricts the movement of the rigid membrane center, and the sensitivity of the main strain gauge drops sharply. The sensitivity of the strain gauges 9, 10, 11 does not change much when the membrane touches the rigid center, since they are located in the central region of the flexible part of the membrane, where The forces exerted by the abutment are small, but some slight change in sensitivity occurs, for example, because of their inaccurate location. Each strain gauge 12, 13 abruptly changes its sensitivity after contacting the hard center and the stop. However, the resistance of the composite strain gauge (12 and 13) varies linearly. This is due to the insensitivity of the composite strain gauge to the force acting on the membrane from the side of the stop. Under the action of this force, the strain gauges 12 and 13 are subjected to equal deformations of opposite signs, and their changes (with equal values of the resistances of the resistors) are equal in magnitude and opposite in sign, so that the resistance value of the composite resistor does not change. Therefore, the bridge circuit (see Fig. 2) has a calibration characteristic that is close to linear in an expanded pressure range, including pressures at which the abutment limits the movement of the rigid center of the membrane. The residual nonlinearity of the calibration characteristic (sensitivity difference before and after the membrane touches the membrane) is eliminated in the case under consideration by changing the resistance value of one of the strain gages 12 or 3 by changing its geometrical dimensions, for example, by processing it with a laser beam. So, if the sensitivity of the sensor at low pressures is greater, then to linearize the calibration characteristic, it is sufficient to increase the resistance strain gauge 12 by an amount .. g, 1 where Ah is the change in resistance of the resistance strain gauge, resistance of the resistance strain resistance 12. changing from small to high pressures, the sensitivity of the main circuit at low pressures. Thus, the proposed sensor allows adjustment of the magnitude of the nonlinearity of the calibration characteristic in an expanded pressure range, which increases the measurement accuracy. Claims of pressure sensor according to auth.st. No. 759876, characterized in that, in order to improve the measurement accuracy, one of the additional strain gauges in EE 1 is made up of a composite of two radially oriented tensor resistors, one of which is located near the border with a rigid center and the other at the border with a collar. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 759876, cl. G 01 L 9/06, 09.01.78.