Strain Gauge

Strain gauges
used to apply electrical measurement
techniques to the measurement of mechanical quantities. As their
name indicates, they are used for the measurement of strain. As a
technical term, “strain” is comprised of tensile and compressive strain,
distinguished by a positive or negative sign. Thus, strain gauges can be
used to detect expansion as well as contraction.
The strain of a body is always caused by an external influence or an
internal effect. Strain can be caused by forces, pressures, moments,
heat, structural changes of the material and the like. If certain
conditions are fulfilled, the amount or the value of the influencing
quantity can be derived from the measured strain value. In
experimental stress analysis, this feature is widely exploited.
Experimental stress analysis uses the strain values measured on the
surface of a specimen or structural part to determine the stress in the
material and also to predict its safety and endurance. Special
transducers can be designed for the measurement of forces or other
derived quantities, e.g., moments, pressures, accelerations,
displacements, vibrations and others. The transducer generally
contains a pressure-sensitive diaphragm with strain gauges bonded to it.
Prime strain gauge
selection
considerations
• gauge length
• number of gauges in gauge pattern
• arrangement of gauges in gauge pattern
• grid resistance
• strain-sensitive alloy
• carrier material
• gauge width