1. Strain Gauges By Ross, James and Peter

2. What is a Strain Gauge? A strain gauge is a sensor that converts force, pressure, tension, weight etc into electrical resistance that can be measured.

3. How does it work Electrical resistance strain gauge The device is made up from a thin wire on a flexible paper tissue. The wire is arranged in a zig-zag configuration The gauge is placed on a test piece with the wires aligned across the direction of the strain to be measure When a force is applied on the test piece, the wire experience a strain and increase in length, therefore the resistance in the wire changes whuch can then be measured. For example; to measure a tensile force the gauge will be placed on the test piece vertically as the force applied will be vertical. When the force is applied the gauge will stretch and the resistance change can be measured

4. Wheatstone Bridge A wheatstone bridge can be set in three different ways: Quarter bridge, half bridge and full bridge A full bridge will have four strain gauges active, a half will have two, and a quarter will have one. A half bridge will use two gauges along with two high precision resistors The benefit of using the full wheatsone bridge is four strains can be measured on opposing sides of the test piece giving a more accurate result.

5. Strain Gauge Formula Strain = change in length/ original length Can be positive (tensile) Or negative (compression) Sensitivity to strain can be expressed as gauge factor (GF) GF= (change in resistance/original resistance)/ (Strain)

6. Applications Tensile testing Pressure Temperature change Torsion Compression Acceleration