Pressure gauges are devices used to measure pressure, all pressure gauges have their own sensing element, which senses the value of the measured quantity.
There are different types of pressure gauge available, common types available are:
Diaphragm pressure sensing element:
The diaphragm is an elastic membrane that elongates when pressure is applied to it. The diaphragm is a single sheet which elongate, Joining two diaphragm to form a capsule.
Two capsules joining to form a stacked diaphragm.
Adding more capsules to the diaphragm increases the sensitivity of the gauge.
When pressure is applied to the diaphragm, it flexes. The movement is transmitted by a link that connects to the pointer. The pointer moves to indicate the amount of pressure applied to the diaphragm. The diaphragm stays at the original position until a pressure is applied to it.
Bellow sensing element:
The below is another type of stacked diaphragm. The stacked diaphragm is made of several sheets, while the bellow is made of single sheet.
The applied pressure makes the bellows expand. The expansion causes the bellows to get longer. When pressure is removed, the bellows get shorter.
The movement of the bellows will be transmitted by a link connected to a pointer. The pointer indicates the pressure applied to the bellows.
The Bourdon tube:
The bourdon tube is the ‘C’ shaped tube shown in the above figure. When a pressure is applied to the tube, the tube stretches outwards. The tube end is attached to a pointer using a link. The link-gear system makes the pointer moves along the scale. The circular motion of the pinion gear drives the position of the pointer to indicate the amount of pressure applied to the Bourdon tube.