What is Strain Gauge? Basics of Strain measurement

What is strain gauge ? how it works?

A strain gauge is used to measure strain.Measurable by measuring its resistance. This is due to its electrical conductance on conductors geometry.

Strain gauge is adhered to the material under stress.

Elongation of the strain gage is measurable.

Substrate could deform due to force,torque,pressure,displacement,acceleration etc…

Applications of Strain Gauge

  1. Experimental stress analysis 2.Measurement of forces Example - Pressure,Acceleration,Displacement,Vibrations

Principle of Operation

When tension applied area narrows and resistance increases.

When compression applied area thickness and resistance decreases.

The change in resistance of device is reasonably linear function on its formation.

It converts mechanical strain to electrical signal.

Elements of Strain Gauge

  1. Wheatstone bridge - Resistance comparing circuit 2.Amplifier - Bring signal to detectable level 3.Detector - Electrically measure the amplified signal 4.Recorder - Convert the detected signal into readable form

Basic Block Diagram of Strain Gauge

Block diagram of Strain Gauge

Possible Error Source

1.Humidity 2.Overloading 3.Lead-Wire Effect 4.Temperature

Humidity - Cause the corrosion of wire Affect the current flow through the strain gauge

Overloading - Elastic limit of the metal strip Conductive metal will be permanently deformed

Temperature - Alter properties of material Affects sensitivity

Lead wire effect - Wiring distance from the detector Contribute internal resistance