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# Strain Gages

**Purpose:** The purpose of this page is to provide a central place to store information on strain gage technology used in PSAS projects.

Strain gages are resistive devices which can be used to measure changes in length, or strain, of materials that occurs as forces are applied to those materials. They can be used on metals, plastics, and even seemingly inflexible materials such as concrete. A strain gage is mechanically bonded (glued) to the material under test so that any change in the length of the material will result in a change in the length of the strain gage. As the strain gage changes in length, there occurs a small change in the resistance of the strain gage. Measured carefully, the resistance change very accurately reflects the change in length of the material under test.

Background on strain gauges:
<http://www.omega.com/literature/transactions/volume3/strain.html>


### Strain gages we use: ###

<http://www.omega.com/Pressure/pdf/SGT_Full-Bridge_Shear.pdf>

...can measure a maximum of 30,000 microstrain for the SGT series
<http://www.omega.com/techref/pdf/STRAIN_GAGE_TECHNICAL_DATA.pdf>

Definition of microstrain: <http://www.unc.edu/~rowlett/units/dictM.html>

### Load Cells: ###

One of the primary reasons we are using strain gages is for measuring tensile or compressive forces in devices called Load Cells. Our load cell designs can be found [[here|load_cells]].


### Strain Gage Amplifiers: ###

Load cells require sensitive amplifier circuits to measure the tiny changes in resistance that is related to strain. Our amplifier designs can be found here (link).