Page 48 - Shellie Suzana Binti Saad
P. 48
STRAIN GAUGE
(UNBONDED)
Normally, it is used for measuring strain or
displacement between a fixed and a moving structure
by fixing four metallic wires as shown in the diagram
above, so that two are in compression and two are in
tension.
The wire is made of various copper nickel, chrome
nickel, or nickel iron alloys.
Usually connected in a bridge circuit with no load
applied to the strain gauges, the bridge is balanced.
When an external load is applied, the resistance
strain gauges change causing an unbalance of the
bridge circuit which results in an output voltage.
This voltage is proportional to the strain.
Unbonded strain gauges are used in force,
pressure, and acceleration measurements.
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