A Mechanical gauge is best to measure High Fluid Pressure,where Tube Gauge cannot be conveniently used.The principle on which all Gauges work is almost same.Following three types of Gauges are more important from subject point of view.
01)Bourdon's Tube Pressure Gauge:-
The Bourdon's Tube Pressure Gauge is most suitable to measure the pressure of fluid,above or below the Atmosphere Pressure.In its simplest form,consists of an elliptical tube ABC,bent into an arc of a circle.
This bent-up tube is connected to the fluid at C (inlet of Fluid),the pressurised fluid flows into the tube,as a result of the increased Pressure,tends to straighten itself.
The tube tends to become circular as it is encased in circular cover.With the help of simple Pinion and Sector arrangement,the elastic deformation of the Bourdon's tube rotates the Pointer.This Pointer moves over a Calibrated Scale.Which directly shows the Pressure.
02)Diaphragm Pressure Gauge:-
This Pressure Gauge is also used to found out the Pressure of a Fluid,above or below Atmosphere Pressure.Instead of Bourdon's tube a Corrugated Diaphragm is used,hence it is called Diaphragm Pressure Gauge.
When the Gauge is connected to the Fluid at C(inlet of Fluid), causes some deformation of the Diaphragm due to fluid pressure.With the help of some Pinion arrangement,the elastic deformation of the Diaphragm rotates the Pointer.This Pointer moves over the Calibrated Scale.Which directly shows the Pressure.
A Diaphragm Pressure Gauge is generally,used to measure relatively Low pressure.
03)Dead Weight Pressure Gauge:-
This type of Pressure Gauge is generally used for the Calibration of the other Pressure Gauge in a Laboratory.In its simplest form,consist of a Piston and a Cylinder of known area and connected to a Fluid by a Tube.
A Pressure Gauge,to be Calibrated,is fitted on the other end of the tube.By changing the Weight,on the Piston,the Pressure on the Fluid is calculated and marked on the Pointer.
By taking adequate precaution,a small error due to Frictional Resistance to the Motion of the Piston,an be avoided.