SU1723472A1 - Pressure difference transducer - Google Patents

Abstract

Usage: measurement of pressure difference in control and regulation systems when measuring small difference of high static pressure. SUMMARY OF THE INVENTION: An elastic sensing element is you: complete in the form of a flat membrane 2 with a cylindrical collar attached to the receiving choke 1 along the perimeter and having annular grooves on the working plane of the membrane, the height of the cylindrical collar being 1/4 .

Description

FI.1

The invention relates to a measurement technique and can be used to measure the pressure difference in control and regulation systems.

An inductive differential pressure transducer is known, containing two bonded bowls with inductors separated by a membrane clamped between the ends of the cups by means of annular projections and a hollow.

The disadvantage of this converter is the impossibility of obtaining stability (constant) calibration characteristic, which provides with high accuracy the measurement of a small difference between high static pressures under the influence of external factors (temperature).

A differential pressure sensor is known, comprising a housing made of a magnetically soft material, a membrane and magnetoresistive transducers mounted on the end portions of the housing located above the center of the membrane.

The disadvantage of this differential pressure sensor is the dependence of the magnetic properties of the material on high static pressures. Magneto-soft materials irreversibly change the magnetic permeability due to high mechanical stresses, the so-called shock effect, i.e., with increasing static pressures, the sensitivity of the sensor to measuring a small difference between high static pressures decreases.

Closest to the proposed technical essence and the achieved result is a pressure sensor comprising a housing (with receiving sockets) and an elastic sensitive element in the form of a flat membrane with perimeter thickenings, the housing and the sensitive element being made of a material with different coefficients of linear expansions.

The disadvantage of this design is the impossibility of obtaining a stable (constant) calibration characteristic when measuring a small difference between high static pressures. The reason for this is the occurrence, when exposed to high static pressures, of significant radial stresses (7g) at the place of sealing a flat membrane, which change the rigidity of the membrane, i.e. its sensitivity, on which the measurement accuracy depends, and with increasing static pressure, the sensitivity decreases,

In addition, the sensor does not provide measurement of a small difference between high static pressures with high accuracy, since to obtain the required sensitivity a thin flat membrane with a ratio of the diameter of the membrane (P) to the thickness of the membrane (h) D / h max, having potential to unstable state is required of the membrane, the so-called

clap effect. Increasing the thickness of the membrane in order to eliminate the effect leads to an increase in the diameter of the membrane to the fourth degree and, consequently, to excessively large overall dimensions,

since the membrane breakdown is determined by the formula:

PD

. where P is the measured pressure difference; D-diameter of the membrane; h-membrane thickness; - E - modulus of elasticity of the material. The aim of the invention is to improve the measurement accuracy of a small difference in high static pressures, to reduce overall dimensions by making an elastic sensing element in the form of a flat membrane with a cylindrical shoulder fixed to the receiving choke along the perimeter and having annular bridges on the working plane of the membrane, and the height the cylindrical collar is 1/4 of the membrane radius.

Figure 1 shows the sensor, a general view; figure 2-node I figure 1.

The sensor consists of a stepped cylindrical sleeve 1 with a receiving nipple of the membrane 2, a housing with a receiving nipple 3 of an inductive converter.

A cylindrical collar is made around the periphery of the membrane 2, with which the membrane is attached, for example, by welding at a step of a smaller diameter of the cylindrical sleeve. On the membrane side of the inductive converter, annular grooves are made. The height of the cylindrical collar is 1/4 of the radius of the membrane.

The device works as follows.

When a pressure difference between PI-P2 is applied to the membrane 2, it bends and changes the parameters of the electromagnetic circuit of the membrane-inductive converter.

The change in pressure is used to determine the pressure difference PI and P2. This option of fixing the membrane 2 with a cylindrical collar allows to provide the same effective membrane areas, washing the entire surface of the membrane, i.e. when changing static & pressure, a change in the rigidity of the membrane does not occur, which ensures a constant calibration characteristic that does not depend on the change in the value of the bilateral static pressure.

Claims (1)

Formula from the brethren .. The differential pressure sensor, comprising a housing with two receiving nipples placed on both sides of the sensing element, made in the form of a membrane and an inductive transducer, which is connected to and from increasing the accuracy of measuring the small difference in high static pressures and decreasing dimensions; a stepped cylindrical bushing with a supporting surface is inserted into it, located on one side of the membrane, on the other side of which is placed an inductive transducer, while the membrane is made with a cylindrical shoulder on the periphery, steps of a cylindrical sleeve of a smaller diameter, and annular grooves are made on the membrane from the inductive converter; height is a cylinder Cesky collar is 1/4 of the radius of the membrane. Phie 2