In this note, we are going to know that What is Strain Gauge? and also the construction of a strain gauge and its types. Welcome to Poly Notes Hub, a leading destination for polytechnic engineering notes.

Author Name: Arun Paul.

What is Strain Gauge?

A strain gauge is a sensor that measures strain (or deformation) in an item. When a material is stretched or compressed, the strain gauge’s electrical resistance changes, which is used to measure strain.

Diagram of a Strain Gauge

Materials of Construction of Strain Gauge

Strain gauges are usually made from metallic alloys or semiconductor materials having stable electrical properties.

Common Materials

1. Constantan (Copper–Nickel Alloy)
   • Most commonly used
   • Good stability
   • Low temperature coefficient
2. Nichrome (Nickel–Chromium Alloy)
   • High resistivity
   • Good corrosion resistance
3. Karma Alloy
   • Nickel–Chromium–Aluminium–Iron alloy
   • Excellent temperature stability
4. Platinum–Tungsten
   • Used for high temperature applications
5. Semiconductor Materials
   • Silicon
   • Germanium

Classification of Strain Gauges or Types of Strain Gauges

Strain gauges are mainly classified into the following types:

1. Mechanical Strain Gauge: Measures strain using mechanical displacement.
2. Electrical Strain Gauge: Measures strain by change in electrical resistance. There are three types of electrical strain gauges.
   • Wire strain gauge
   • Foil strain gauge
   • Semiconductor strain gauge
3. Optical Strain Gauge: Uses light interference to measure strain.
4. Pneumatic Strain Gauge: Measures strain through changes in air pressure.