The operating principle of diaphragm element is similar to that of the bellows. The pressure to be measured is applied to diaphragm, causing it to deflect, the deflection being proportional to the applied pressure. The movement of diaphragm depends on its thickness and diameter.The movement is small and hence a diaphragm element does not require any spring as in the case in bellows.
The movement of diaphragm is a convenient way of sensing a pressure. The unknown pressure Is applied to one side of diaphragm.
The edge of the diaphragm is rigidly fixed and cause deflection on account of the applied pressure. The displacement of the diaphragm may be measured to determine the value of applied pressure.
The diaphragm, which is a very thin membrane under pressure and therefore under radial tension, may use capacitive or inductive transducer, to produce an electrical output which is proportional to the output of the transducers.
The use of Diaphragms using thin membrane is limited to measurement of low level pressure fluctuations and are suitable for resistance and piezoelectric transducer which require greater displacement than are produced by membrane.
⇒Diaphragm are of three type
- Flat type
- Corrugate type
- Capsule type
A corrugated type diaphragm on account their increased surface are give greater deflections, typically 2% of the diaphragm diameter.