SU1767375A1 - Pressure difference pickup - Google Patents

Abstract

Use: for measuring static and dynamic pressures of liquid and gaseous media. The goal is to improve the measurement accuracy by reducing the temperature error. SUMMARY OF THE INVENTION: The sensor comprises an evacuated housing 1, a cylindrical base 2 in which a cavity 3, limited by the first measuring membrane 4, and a cavity 5, limited by the second measuring membrane 6, are made. The cavity 3 has access to the pressure Pi. The cavity 5 has access to the pressure P2 through the channel 7 and is isolated from the pressure Pi by the plate 8. Opposite the membranes 4 and 6 there is a fixed disk 9 with a gap. On the planar side of the base 2 (on the membranes 4 and 6), circular electrodes 11 and 12 of the measuring capacitors with capacitance Cxi and СХ2 are formed through the dielectric layer. and on the non-deformable part of the base 2 - circular electrodes 13 and 14 of the reference capacitors with a capacity of Coi, C02- Electrodes are formed on the disk 9 in a mirror image through another dielectric layer. A fitting 16 is welded to the connection of the sensor with the main to the cylindrical base 2. The proposed meter has an increased measurement accuracy by a factor of 2-3. 1 il. cl

Description

The invention relates to a measurement technique, in particular to capacitive differential pressure sensors, and can be used to measure the static and dynamic pressures of liquid and gaseous media.

A capacitive pressure sensor is known, comprising two flat membranes with edge sleeves facing one another with ends between which there is a metal stationary disk, which is clamped in the housing with the help of two washers made of electrically insulating material.

A disadvantage of the known construction is the low measurement accuracy due to the fact that the distance between the electrodes of the two capacitances is set by two washers and that the distance between the electrodes is unevenly affected by temperature, which causes false changes in the output signal. In addition, the absence of reference capacitances that are in the same operating conditions as the measuring capacitances does not allow for the high accuracy of pressure differential measurements in a wide temperature range.

The purpose of the invention is to improve the measurement accuracy by reducing the temperature error.

The goal is achieved by the fact that the differential pressure sensor containing

VI about VJ from XI cl

two identical flat membranes and a fixed disk mounted with a gap relative to the membranes, a cylindrical base is inserted in which supply channels are made, the membranes are made in the same plane of the end surface of the cylindrical base, and circular measuring electrodes are formed on the membranes through the dielectric layer on the undeformable base part there are two introduced supporting circular electrodes, while on the disk in a mirror-symmetric display through a dielectric layer o Vanir four circular stationary electrode.

1 schematically shows a differential pressure sensor; Figures 2 and 3 are sections A-A and BB in Fig. 1 (topology of electrode placement).

The pressure sensor includes an evacuated body 1, a cylindrical base 2 in which a cavity 3, limited by the first measuring membrane 4, and a cavity 5 limited by the second measuring membrane 6, are made. The cavity 3 has access to the measured medium from the main. The cavity 5 is connected by a channel 7 and is isolated from the cavity 3 by a plate 8. A disk 9 with a gap is installed opposite the membranes 4 and 6, the size of which is determined by the thickness of the ring 10. On the planar side of the base 2 (on the membranes 4 and 6) circular electrodes 11 are formed through the dielectric layer and 12 measuring capacitors with a capacity of Cxi, CX2. and on the non-deformable part of the base 2 - circular electrodes 13 and 14 of the reference capacitors with a capacity of Coi, Co2- On the disk 9 in the mirror image through another dielectric layer the electrodes 15 are also shaped in the form, as well as on the base 2. To connect the sensor to the main the cylindrical base 2 is welded fitting 16.

The sensor was developed using a planar-film technology of forming metal-dielectric-metal (electrode) structures on a membrane and, in one design, contains two measuring channels for recording pressures PI and Pa with subsequent recording of pressure differences Rraz.

The sensor works as follows.

The pressure Pi is supplied through the nozzle 16 into the cavity 3, and the membrane 4 bends by an amount proportional to the absolute value of PL. The value of the measuring capacitance changes by the AC value (1 proportional to PL) The Cxi value is recorded by the converter in the form of an output voltage Uix proportional to the Coi / Cxi ratio .

Ulx uo ()

0)

where Ki is the conversion factor for electronic equipment;

Do is the initial reference signal.

Pressure P2 is fed through channel 7 into cavity 5. Membrane 6 bends by an amount proportional to pressure PZ. The magnitude of the measuring capacitance CX2. associated with membrane 6, changes to the AC value (2. proportional to P2.

The value Cx2 is recorded by the second channel of the converter as the second voltage U2Xl proportional to the ratio Coi / Cxi:

U2x Uo (K2-%

W9

(2)

where K2 is the conversion factor for electronic equipment.

The electronic converter carries out periodic balancing of the charges on capacitors C0-, Cxi, € 02, Cx2, converts them into voltages Uix and U2X, and in a subtractive device generates a voltage 11w, proportional to the difference (Uix-U2x):

  Uix - U2x Cs (Ki) (K2) N P1 - P2 Rraz,

(3)

where Кз, К4, N - scale factors of blocks of the electronic converter.

Thus, an output signal proportional to the pressure difference is obtained at the output of the sensor.

The proposed sensor differs from the known increased by 2-3 times the accuracy of measurement.

Claims (1)

Invention Formula A differential pressure sensor containing two identical flat membranes and a fixed disk mounted with a gap relative to the membranes, distinguishing so that, in order to improve accuracy by reducing the temperature error, a cylindrical base is inserted into it, in which the feed channels , the membranes are made in one PPB of the end face of the overTTTostTG of the cylindrical base, while on the membranes, measuring circular electrodes are formed through the dielectric layer, and the undeformable part of the base has two inserted supporting circular electrodes, while on the disk in the mirror four circular stationary electrodes are formed by symmetric mapping through the dielectric layer. Ch2 : Uchuu hhchu Hhcu /five