The small term ‘strain’ is used in Science and engineering to imply stress that is caused by force. It can be defined as the alteration of length, produced by force is divided by the original length of the material. For instance, for 10 cm elastic that stretches 1 cm, the strain is calculated to be 0.1. If you are wondering, what happens with the application of strain? Well, it primarily changes the shape and has a tendency to longer, when the elastic is pulled apart. On the contrary, the length of the material gets reduced when pulled towards each other. A strain gauge is a small device that measures the change in shapes when the force is exerted towards same direction or force is applied on separate directions.

What is strain gauge?

Strain gauge is an innovative device that is very simple, yet complex. It is used commonly by scientists and engineers while working on certain projects. Strain gauges are a geotechnical tools that are used in various projects to measure strain. Some of the common place it is used is underground cavities, tunnels, buildings, concrete, masonry dams, and bridges, and for embedment in soil or concrete. Strain gauge basically determines stress indirectly and the quantitative variation with time. The deviation in stress is measured by multiplying the measured strain by elasticity.

Strain gauge is also known as strain gage. It is a device used to measure the strain of an object and it is invented by E. Simmons and Arthur C. Ruge in 1938. People can determine the gauge factor of an object by using a strain gauge. 

A Basic Background about Strain Gauge:

This device functions on the basis of the principles of Piezoresistive effects. It is a transducer that measures strain, stress, displacement, force and pressure. These significant sensors vary with applied force that plays a crucial role in converting the varied parameters like force, pressure, tension, weight, etc into resistance. This resistance can be measured later. However, while changing the resistance, the shape and size of the material also alters.

The strain gauge comprises insulating flexible backing that is supported by a metallic foil pattern. These gauges are connected to the respective object under stress with the use of adhesive. The foil of the object gets deformed, resulting in altering the electrical resistivity of the foil. Wheatstone bridge measures the change in resistivity. The strain is co-related with the strain by a quantity called the gauge factor.

Different Categories of Strain Gauges:

There are varied types of strain gauges in action as mentioned below.

  • LY Linear Strain Gauges: This type of gauge measures the strain in one way or one direction. The varied categories of LY linear strain gauges have different sizes. For instance, the DY11, DY13, DY1x, DY41, DY43, DY4x, are the double linear strain gauges.
  • Strain Gauge Rossettes: This category is common and it is available in varied styles like membrane rosette, tee rosette, rectangular rosette, and delta rosette.  The first category of strain gauge rosettes is membrane rosette strain gauge that is used to measure displacement, pressure, force and the elastic strain of materials and structures. This membrane gauge is used in railroad car manufacturing, mechanical engineering, aircraft, and missile production, and other industries.
  • Tee Rosette Strain Gauge (0-900): This type of gauge comes with two distinct grids that are mutually perpendicular. One sub – category is rectangular rosette (0- 450-900), it comprises of three grids. Another sub-category is called delta rosette, also called three-element delta rosette strain gauges. What distinguishes both the sub-categories is the fact that tee rosette is rectangular in shape and displaces 450 and 900 because of its angular third grids. Whereas, delta rosette displaces the second and third grids 600 and 1200 away from the first grid.


Thus, this fundamental feature is used for geotechnical monitoring and follows the principles mentioned above in mechanical, optical, acoustical, pneumatic or electrical industries.