30-01-2013, 02:31 PM
Presentation on Pressure Sensing Elements
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Pressure Sensing Elements
Measurement of pressure Basically involves two steps:-
Translate the pressure into mechanical displacement
Sense the Mechanical displacement
Mechanical Type Pressure Sensors
These are basically of 3 types:
Bourdon type
Bellows
Diaphragms
Bourdon Type Pressure Gauge
The Bourdon pressure gauge uses the principle that a flattened tube tends to straighten or regain its circular form in cross-section when pressurized.
Bourdon Tubes are also divided into three
categories:
C Bourdon
Spiral type
Helical Type
Bellows
Made of Bronze, etc..
The movement is proportional to number of convolutions
Sensitivity is proportional to size
In general a bellows can detect a slightly lower pressure than a diaphragm
The range is from 0-5 mmHg to 0-2000 psi
Accuracy in the range of 1% span
Diaphragm
A diaphragm usually is designed so that the deflection-versus-pressure characteristics are as linear as possible over a specified pressure range, and with a minimum of hysteresis and minimum shift in the zero point.
Figure shows the
Flat and corrugated
Type diaphragm.