Pressure transducers and elements – electrical
The typical range of transducers here is:
– Strain gauge
– Vibrating wire
– Linear Variable Differential Transformer
Strain gauge sensing uses a metal wire or semiconductor chip to measure
changes in pressure. A change in pressure causes a change in resistance
as the metal is deformed. This deformation is not permanent, as the
pressure (applied force) does not exceed the elastic limit of the metal. If
the elastic limit is exceeded than permanent deformation will occur.
This is commonly used in a Wheatstone bridge arrangement where the
change in pressure is detected as a change in the measured voltage.
Strain gauges in their infancy were metal wires supported by a frame.
Advances in the technology of bonding materials mean that the wire can
be adhered directly to the strained surface. Since the measurement of
strain involves the deformation of metal, the strain material need not be
limited to being a wire. As such, further developments also involve metal
foil gauges. Bonded strain gauges are the more commonly used type.
Figure 2.12 shows simple Wheatstone circuit for strain gauge.
As strain gauges are temperature sensitive, temperature compensation is
required. One of the most common forms of temperature compensation is
to use a wheatstone bridge. Apart from the sensing gauge, a dummy
gauge is used which is not subjected to the forces but is also
affected by temperature variations. In the bridge arrangement the dummy gauge
cancels with the sensing gauge and eliminates temperature variations in the
(excerpt from Engineering Institute of Technology)