Strain is a measure of the deformation of a material or structural member subjected to an external load or force. Strain is defined by:

e = DL/L0


where e is the strain, DL is the change in linear length and L0 is the original linear length of the material. For many engineering materials the strain is a small number and is multiplied by a million and is expressed in microstrain units or parts per million.


Strain can be measured and calibrated to measure force or pressure in strain gauge based measuring systems. Electrical gauges based on electrical resistance, piezoresistance, capacitance, inductance piezoelectricity or photoelectricity are used to measure strain. Simple resistive type strain gauges are generally the most popular type of strain gauge. They have advantages in size, mass and cost over other types of strain gauges. Inductive and capacitative strain gauges are generally more rugged, and able to maintain calibration over an extended period of time, and are more likely to be used for permanent installations and specialized applications. Semiconductor and piezoresistive strain gauges are sensitive to strain but tend to be nonlinear and sensitive to temperature changes.


Return to the Introduction

Move back to Transducers and their Applications

Move forward to Electrical Resistance Strain Gauge 

Support for the development of this module was provided by the National Science Foundation and The Cooper Union for the Advancement of Science and Art.

Please send questions or comments to Professor Ron Adrezin or Professor Daniel Raichel.