SU1744540A1 - Capacitive pressure pickup - Google Patents

Abstract

The invention relates to a measurement technique, in particular to capacitive pressure sensors, and makes it possible to increase the sensitivity of the sensor. The pressure sensor contains a membrane 1 with a rigid center 2, made in one piece with the housing 3, on which the electrode 4 of the working capacitor and the electrode 5 of the reference capacitor are placed, the plate 6 with elastic jumpers 7, fastened centrally with the hard center 2 and peripherally to the housing 3. A movable electrode 10 of a working capacitor and an electrode 11 of a reference capacitor are mirrored symmetrically on the plate 6. Moving the electrode 10 to the periphery of the movable part of the plate 6 makes it possible to reduce the radius of the hard center 2 and increase the sensitivity of the sensor. 2 Il.

Description

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The invention relates to a measurement technique, in particular to pressure sensors, comprising a capacitive pressure-to-electrical transducer.

A capacitive pressure sensor is known, which contains a rigid center membrane, which is made in one piece with a housing, which is one of the electrodes of the working capacitor. A rigid plate is fastened to the rigid center of the membrane, consisting of a central circle and an annular form located on the periphery of the second electrode, which are separated by an insulator.

The disadvantage of this sensor is the low measurement accuracy due to large values of temperature error and linearity error. The reason for the temperature error is the change in the gap between the electrodes during temperature fluctuations, the reasons for the linearity error are the hyperbolic dependence of the capacitance on the gap and the location of the part of the second electrode of the working capacitor above the deformed section of the membrane.

The closest to the proposed one is a membrane with a rigid center, which is made in one piece with the housing, onto which the working capacitor electrode is in the form of a circle and an annular electrode of the reference capacitor, placed on a thick non-deformable part of the housing, using microelectronic technology. The stationary electrodes of the working and reference capacitors, also manufactured using microelectronic technology, are arranged mirror-symmetrically on a plate in the form of a disk attached to the housing at at least three points.

The conversion function of such a sensor in combination with a secondary transducer based on a hyperbolic measuring circuit is

With

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where K is a constructive factor;

Co, Cx of the capacitance, respectively, of the reference and working capacitors.

The use of such a transformation and thin-film electrodes can significantly reduce the temperature error and linearity error.

A disadvantage of the known sensor is the low relative sensitivity, depending on the ratio of the radius of the hard center r to the radius of the membrane R. To increase the sensitivity, it is necessary to reduce the radius of the hard center relative to the radius of the membrane. However, the capacitance of the operating capacitor decreases in proportion to the square of the radius of the hard center (radius of the electrode of the operating capacitor), which drastically reduces the capacitance of the operating capacitor, and hence the sensitivity of the sensor to the measured value.

The aim of the invention is to increase the sensitivity of the sensor.

To achieve this goal, the plate is divided into central movable and stationary peripheral parts interconnected by elastic bridges, the central movable part of the plate is rigidly fixed in the center with the membrane, and the working capacitor electrodes are made in the form of rings and are located respectively on the periphery of the movable plate part and on non-deformed part of the hull.

Figure 1 shows the design of the proposed pressure sensor; figure 2 - topology deposited on the electrode plate of the working capacitor and the electrode of the reference capacitor.

The sensor contains a membrane 1 with a hard center 2, made in one piece with the housing 3, which houses the electrode 4 of the working capacitor and the electrode 5 of the reference capacitor, plate 6 with jumpers 7, bonded in the center with a hard center 2 by spot welding 8 and along the periphery body spot welding 9. On the plate mirror-symmetrically located mobile electrode 10 of the working capacitor and the electrode 11 of the reference capacitor.

The electrical output of the working capacitor electrode is made by jumper 7.

The capacitive pressure sensor operates as follows.

When pressure is applied to the cavity of the housing 3, the membrane 1 bends and moves the movable part of the plate 6 fixed to the rigid center 2. The capacity of the operating capacitor decreases. Elastic jumpers 7 practically do not interfere with the movement of the membrane and the moving part of the plate, since their total stiffness is much less than the stiffness of the membrane. When using a secondary converter with a conversion function (1), the output voltage will be proportional to the movement of the moving part of the upper plate. Linearity error will only be determined by non-linear

dependence of membrane deflection on pressure. When the temperature fluctuates, the initial gap between the working and reference capacitor electrodes changes by the same amount, which drastically reduces the temperature error.

You nose of the working capacitor electrode 10 to the periphery of the movable part of the plate 6 reduces the value of the radius of the hard center 2 to values that secure the movable part of the plate 6 with the hard center, and thereby increase the sensitivity of the sensor.

Claims (1)

Claims of Invention A capacitive pressure transducer comprising a rigid center membrane, a first thin film electrode of a working capacitor, a first thin film annular electrode of a reference capacitor, and a disk bonded on the periphery with a housing, are applied to the body. the second thin-film electrodes of the working and reference capacitors are mirrored symmetrically, characterized in that, in order to increase the sensitivity, the plate is divided into central movable and stationary peripheral parts interconnected by elastic bridges, with the central movable part of the plate fixedly centered with membrane as well The working capacitor electrodes are made in the form of rings and are located respectively on the periphery of the movable part of the plate and on the non-deformable part of the body. 7