CN1431472A - Fixed type self vibration damping difference flow sensor - Google Patents

Abstract

The senso rincludes the detection units fixed on the two sides of the flat plate symmetrically. Each detection unit includes the body case possessing the through hole parallel to the axis m-m of the flat plate. The male tab in the middle of the through hole divides the through hole into upper and lower symmetrical space intervals. The elastic membranes seal the two ends of the through hole. There are the piezoelectric ceramic sheet and the insulation quality block between the tab and the ceramic sheet in each space interval. One end of each ceramic sheet is fixed on the elastic membrane. The connected lead wires of the two ceramic sheets are leaded out through the axial out hole of the flat plate. The sensor possesses the sensitivity, strong antivibration ability, large range and high reliability.

Description

Fixed self-damping differential flow sensor

Technical field

The present invention relates to flow sensors, especially self-damping differential flow sensors.

Background technique

In the late 1960s, new instruments that applied the principle of fluid vibration to measure flow appeared successively. For example, vortex flowmeters, jet flowmeters, and vortex precession flowmeters all belong to liquid vibration flowmeters. They pass heat-sensitive, strain, Flow sensors with detection methods such as capacitance and ultrasonic waves can detect fluid vibration frequency signals that are proportional to volume flow. For vibrating flow sensors, the vibration problem is an important indicator to measure the industrial application of a vibrating flow meter. Vibration in industry is ubiquitous, such as speed pulsation and fluid oscillation in fluid turbulence, and random factors such as industrial pipeline vibration, valve opening and closing, and valve core vibration, which will cause great noise to the detected frequency signal interference. At present, the more advanced vibration flow sensors have certain anti-vibration capabilities. However, the detection elements of these sensors are all fixed on the pipe wall, and the ability to resist pipeline vibration is limited. In addition, for the interference of fluid vibration, when the vibration direction of the vibration noise is parallel to the vibration direction of the measured frequency signal (that is, vibrating in the same direction), the anti-interference ability of these flow sensors is relatively weak, and the output signal will be mixed with a lot of noise. This phenomenon is especially obvious when measuring small flow rates.

Contents of the invention

The purpose of the present invention is to provide a fixed self-damping differential flow sensor with high measurement sensitivity and strong anti-interference.

The fixed self-vibration differential flow sensor of the present invention includes detection units symmetrically fixed on both sides of the plate, each detection unit includes a housing, and the housing has a through hole parallel to the axis m-m of the plate, with a handle in the middle of the through hole The hole is equally divided into upper and lower two symmetrical sections of the boss, the aperture of the two symmetrical sections is larger than the hole diameter of the boss, there is a channel at the boss to communicate with the axial outlet hole of the plate, and the two ends of the through hole are respectively sealed by elastic diaphragms , each section has a piezoelectric ceramic sheet and a ring-shaped insulating mass, one end of the piezoelectric ceramic sheet is fixed to the elastic diaphragm, the insulating mass block is sandwiched between the boss and the piezoelectric ceramic sheet, the piezoelectric ceramic sheet and the insulating mass There is a gap between the periphery of the block and the wall of the through hole, and the lead wires of the upper and lower piezoelectric ceramic sheets are connected and drawn out from the outlet hole of the plate through the channel.

The sensor of the present invention has high measurement sensitivity, and can still give a strong detection signal by using the differential principle when the flow rate is small, and its internal structure has a self-vibration damping function, and has strong anti-interference and large range range , high reliability.

Description of drawings

Figure 1 is an axial half-sectional view of a fixed self-damping flow sensor;

Fig. 2 is the application schematic diagram of the present invention in the vortex flowmeter;

Fig. 3 is a schematic diagram of the application of the present invention in a vortex precession flowmeter.

Detailed ways

Referring to Figure 1, the fixed self-damping flow sensor includes detection units symmetrically fixed on both sides of the plate 6, each detection unit includes a housing 5, in order to obtain a more stable signal, a semi-cylindrical housing is generally used, and the housing 5 has A through hole 7 parallel to the axis m-m of the plate. There is a boss in the middle of the through hole 7 that divides the through hole into two symmetrical sections up and down. The apertures of the two symmetrical sections are larger than the aperture of the boss. The axial outlet holes 4 of the plate are in communication with each other, and the two ends of the through hole 7 are respectively sealed by elastic diaphragms 1, and there are piezoelectric ceramic sheets 3 and ring-shaped insulating ceramic blocks 2 in each interval, and one end of the piezoelectric ceramic sheet is connected to the elastic diaphragm. The diaphragm 1 is welded, the insulating ceramic block 2 is sandwiched between the boss and the piezoelectric ceramic sheet, and there is a gap between the piezoelectric ceramic sheet 3 and the periphery of the insulating ceramic block 2 and the wall of the through hole. The lead wires of the upper and lower piezoelectric ceramic sheets are connected and drawn out from the plate outlet hole 4 through the channel 8 . The four piezoelectric ceramic pieces in the two detection units have the same size, quality, sensitivity coefficient, and equal pre-tightening force, and the four insulating ceramic blocks also have the same size and quality.

The specific application of the present invention is referred to Fig. 2, Fig. 3.

Fig. 2 is the application of the present invention in the vortex flowmeter, in order to measure the flow of the vibrating fluid, the fixed self-damping flow sensor B of the present invention is installed in the back of the vortex generator A in the vortex flowmeter, the sensor and the vortex The generating body is parallel; for the vortex precession flowmeter shown in Figure 3, the fixed self-damping flow sensor should be installed at the front end of the flow channel expansion section, and the axis m-m of the sensor plate intersects perpendicularly with the axis of the pipe.

During operation, the entire sensor is immersed in the fluid. When the vortex flows through the sensor, the alternating pressure generated by the vortex directly acts on the elastic membranes of the two detection units, causing the piezoelectric ceramic sheet to generate alternating charges. At this time, the two detection units will output regular sinusoidal signals S1 and S2. The frequency of these two signals is equal and the phase difference is 180°. When using the differential output, a stronger detection signal can be obtained.

When the fluid oscillates due to random factors such as pipeline vibration and valve opening, it will cause the elastic diaphragm or the sensor housing to generate following vibration. This makes the upper and lower symmetrical piezoelectric ceramics in the detection unit be pressed and pulled respectively, so the two piezoelectric ceramics will generate equal positive and negative charge signals, and when the signals of the upper and lower piezoelectric ceramics are in phase Over time, the charge signals generated by the disturbing vibration will cancel each other out, so the sensor acts as a self-damping vibration.

In addition, for the sensor of the present invention, the pipeline vibration belongs to the same direction vibration, and the sensor uses two detection units for differential detection, so the interference signals of the same direction vibration will cancel each other in the output signal S1-S2, so that Effectively eliminate the interference of pipeline vibration on the detection signal. For the fluid vibration caused by fluid pulsation, it is a series of plane waves propagating with the flow direction in the pipeline, and the pressure caused by it acts on the two detection units of the sensor in the same direction at the same time, which belongs to the same direction vibration interference. Similarly, the differential detection principle of the sensor can eliminate the interference of fluid pulsation on the detection signal. Therefore, the flow sensor of the present invention has high anti-interference ability in flow measurement. It is suitable for flow measurement of vibrating fluids such as liquid, gas and steam.

Claims (5)

1. fixed from vibration damping difference current quantity sensor, it is characterized in that comprising that symmetry is fixed on the detecting unit on flat board (6) two sides, each detecting unit comprises housing (5), housing (5) has the through hole (7) parallel with dull and stereotyped axis m-m, there is in the middle of this through hole (7) one through hole is divided into the boss of two symmetric intervals up and down, the aperture of two symmetric intervals is greater than aperture, boss place, the boss place has passage (8) to be connected with the axial wire hole (4) of flat board, flexible diaphragm (1) sealing respectively of the two ends of through hole (7), piezoelectric ceramic piece (3) and annular insulating matter gauge block (2) are arranged respectively in each interval, one end of piezoelectric ceramic piece and flexible sheet (1) are fixing, insulating matter gauge block (2) is clipped in the middle of boss and the piezoelectric ceramic piece, leave the gap between the periphery of piezoelectric ceramic piece (3) and insulating matter gauge block (2) and the through-hole wall, the lead-in wire of two piezoelectric ceramic pieces (3) joins and draws from dull and stereotyped wire hole (4) through passage (8) up and down.

2. described fixed from vibration damping difference current quantity sensor by claim 1, it is characterized in that said insulating matter gauge block (2) is the insulating ceramics piece.

3. described fixed from vibration damping difference current quantity sensor by claim 1, it is characterized in that size, quality and the sensitivity coefficient of four piezoelectric ceramic pieces (3) in two detecting units is all identical.

4. by claim 1,2 described fixed, it is characterized in that four masses (2) in two detecting units have identical size and quality from vibration damping difference current quantity sensor.

5. described fixed from vibration damping difference current quantity sensor by claim 1, it is characterized in that said housing (5) is half-cylindrical.

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