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technical article
Description of the double needle pressure gauge
2011-12-26 9:10:39

用途说明: Dual needle pressure gauge use description:

The double needle pressure gauge is mainly suitable for measuring the pressure of hydraulic systems or storage cylinders on rolling stock; it can also be used for non-corrosive, non-structural and solidified medium pressure measurement of copper alloy brazing. Meter can measure two same or different at the same time

(The difference between the two should generally not be greater than 1/3 of the limit on the scale range).

Definition of stress:


The concept of pressure here actually refers to the pressure in physics, that is, the magnitude of the pressure on a unit area.


Absolute pressure: The pressure is higher than the absolute zero based on the absolute zero.


Positive pressure: A pressure higher than atmospheric pressure based on atmospheric pressure.


Negative pressure (vacuum): A pressure lower than atmospheric pressure based on atmospheric pressure.


Differential pressure: The difference between two pressures.


Gauge pressure: A pressure that is greater or less than atmospheric pressure based on atmospheric pressure.


Pressure gauge: A gauge that is based on atmospheric pressure and is used to measure less than or greater than atmospheric pressure.


Pressure gauges: In the process of industrial process control and technical measurement, mechanical pressure gauges have become more and more widely used due to their high mechanical strength and ease of production.


The elastic sensitive element in the mechanical pressure gauge is elastically deformed as the pressure changes. The mechanical pressure gauge adopts spring tube (Bourdon tube), diaphragm, diaphragm box and bellows and other sensitive components and is classified according to this. The measured pressure is generally regarded as relative pressure.

Generally, the relative point is selected as atmospheric pressure. The elastic deformation of the elastic element under the action of the medium pressure is enlarged by the gear transmission mechanism of the pressure gauge, and the pressure gauge will show the relative value (high or low) relative to the atmospheric pressure.

The pressure value in the measurement range is displayed by the pointer, and the indication range of the scale is generally made 270 degrees.


Classification of pressure gauges: According to their measurement accuracy, pressure gauges can be divided into precision pressure gauges and general pressure gauges. The accuracy levels of precision pressure gauges are 0.1, 0.16, 0.25, and 0.4; the accuracy levels of general pressure gauges are 1.0, 1.6, 2.5, and 4.0.

Pressure gauges are divided into general pressure gauges, absolute pressure gauges, and differential pressure gauges according to the basis of their indicated pressure. General pressure gauges are based on atmospheric pressure; absolute pressure gauges are based on absolute zero pressure; differential pressure gauges measure the difference between two measured pressures.


按其测量范围,分为真空表、压力真空表、微压表、低压表、中压表及高压表。 Pressure gauges are divided into vacuum gauges , pressure vacuum gauges , micro pressure gauges , low pressure gauges , medium pressure gauges, and high pressure gauges according to their measurement ranges. Vacuum gauges are used to measure pressure values below atmospheric pressure; pressure vacuum gauges are used to measure pressure values below and above atmospheric pressure;

Micro pressure gauges are used to measure pressure values less than 60000 Pa; low pressure gauges are used to measure pressure values from 0 to 6 MPa; medium pressure gauges are used to measure pressure values from 10 to 60 MPa; high pressure gauges are used to measure pressure values above 100 MPa.


The housing of the shock-resistant pressure gauge is made of a fully sealed structure, and the housing is filled with damping oil. Due to its damping effect, it can be used in measuring places where the working environment is vibrating or the medium pressure (load) is pulsating.

The pressure gauge with electric contact control switch can realize alarm or control function.


The pressure gauge with remote transmission mechanism can provide electrical signals (such as resistance signals or standard DC current signals) required in industrial engineering.

The isolator (chemical seal) used in the diaphragm meter can isolate the measured medium from the instrument through the isolation diaphragm in order to measure the pressure of strong corrosion, high temperature, and easily crystallized media.

Elastic element of pressure gauge The elastic sensitive element in the mechanical pressure gauge is elastically deformed as the pressure changes. Mechanical pressure gauges use sensitive components such as spring tubes (bourdon tubes), diaphragms, capsules and bellows and are classified according to this. Sensitive components are generally made of copper alloy,

Stainless steel or made of special materials. 

 
Spring tube (Bourdon tube) is divided into C-type tube, coil spring tube, spiral tube and other types. Generally, cold-work hardened material blank tubes are used, which have a high degree of plasticity in the annealed state, and obtains high elasticity and strength after cold working hardening and qualitative treatment.

Under the pressure of the inner cavity of the spring tube, the elastic characteristics of the spring tube can be used to conveniently convert the pressure into the elastic displacement of the free end of the spring tube. The measuring range of spring tube is generally 0.1MPa ~ 250MPa.


The diaphragm sensitive element is a circular diaphragm with a wave. The diaphragm itself is located between the two flanges or welded on the flange or the edge is sandwiched between the two flanges. The diaphragm is under pressure from the measuring medium. In this way, the small bending deformation of the diaphragm can be used

Indirectly measure the pressure of the medium. The amount of pressure is indicated by the pointer. Compared with Bourdon tube, the diaphragm has larger transmission force. Because the diaphragm itself is fixed around the edges, its vibration resistance is good. The diaphragm pressure gauge can achieve high over-pressure protection (for example, the diaphragm is attached to the upper flange).

The diaphragm can also be added with a protective coating to improve corrosion resistance. Using open flanges, flushing, openings and other measures, diaphragm pressure gauges can be used to measure very viscous, unclean and crystalline media. The pressure measurement range of the diaphragm pressure gauge is 1600Pa ~ 2.5 MPa.  Capsule sensor

It consists of two pairs of diaphragms with a circular wavy cross-section. The pressure of the measuring medium acts on the inside of the capsule cavity, and the resulting deformation can be used to indirectly measure the pressure of the medium. The magnitude of the pressure value is displayed by the pointer. The capsule pressure gauge is generally used to measure the micro pressure of gas.

And has a certain degree of over-voltage protection. The stacking of several capsule sensitive elements will produce a large transmission force to measure extremely small pressures. The pressure range of the capsule pressure gauge is from 250Pa to 60000Pa.

结构原理 Structure principle of double needle pressure gauge


The working principle of the instrument is based on the elastic deformation of the elastic element (spring tube in the measurement system). That is, under the action of the measured pressure, the ends of the two spring tubes are caused to have corresponding displacements, and the gear rods are used to drive and magnify the transmission through the gear transmission mechanism.

The red and black pointers on the fixed gear shaft track the two measured values on the dials respectively;