Sensors are devices that change their shapes when Pressure
is applied.
There are some types of pressure sensor.
1)
Diaphragm
2)
Capsule
3)
Bellows
4)
Bourdon tubes
I.
(C-type)
II.
Helical
III.
Spiral
v Diaphragm
The Diaphragm is one of the three types of elastic
element of pressure sensor
A Diaphragm is consisting
a thin layer or film of material.
Applied pressure causes a displacement of
diaphragm and this movement is measured by displacement transducer.
- Ranges;
|
Absolute Pressure
|
Up to 50 Bar
|
|
Gauge Pressure
|
Up to 2000 Bar
|
|
Differential Pressure
|
Up to 2.5 Bar
|
- Materials of Diaphragm
|
Materials
|
Specification
|
|
Plastic \ Rubber
|
Cheap
|
|
Metal
|
Better Accuracy
|
|
Stainless steel
|
High Temp. Corrosive Range (700 MPa)
|
|
Ceramic
|
Good for Strong Acid \ Alkali's
|
- Magnitude of diaphragm
Normally the
magnitude of diaphragm displacement is 0.1mm.
v Capsule
Capsules are
two diaphragms are joined back to back. Pressure applied on space between the
diaphragms and forcing them to expand. And a transducer is attached for
measuring the deflection of Capsule. The deflection of capsule is depends on its,
Diameter, thickness and elasticity.- Materials
1.
Stainless steel
2.
Iron nickel
alloy
3.
Phosphor bronze
Pressure range of capsule using these materials is up to 350 kpa.
Capsule can
be joined together for increasing sensitivity.
v Bellows
In Bellows
the diaphragm is separated by a corrugated tube.
Bellows is
the most sensitive for Low pressure measurement [0 to 210 kpa].
When Pressure applied on Bellows it produced transitional
motion on end of the bellows and that can be measured by transducer.
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