Pressure Transducer

OBJECTIVES

Explain the general principle of operation, give limitation of, and explain the various circuits used in the following pressure transducers:

·         strain gauge pressure transducers.

·         capacitive pressure transducers.

·         piezoelectric pressure transducers.

·         magnetic pressure transducers.

·         optical pressure transducers.

·         piezoresistive pressure transducers.

·         resonant wire pressure transducers.

Pressure Sensors and Transmitters 

Measuring instruments can be functionally broken down into four general blocks.

  (Ref : NAIT Sheet 1995)

The  sensor receives some energy from the measured medium and converts this energy into another form that is compatible to the next part of the instrument.  This may involve one step or several steps with transmission of the energy between them.  The variable manipulation step allows the signal to be changed so that it can be delivered or presented in a meaningful way.  This step also allows for the calibration of the signal.

Strain Gauge Pressure Transducers

The strain gauge is a device for measuring mechanical surface strain.  It is used for a wide variety of applications, making it possibly the most used transducer in the measurement field.  Strain is defined as the ratio of length extension of a conductor to its original length.

Strain is the elastic movement of a material due to an applied force.  If the strain is positive, then we say the material is under tension.  If the strain is negative, then we say the material is under compression.

A strain gauge then is a device that measures this change in length or strain.