Strain Gauge

A strain gauge is a device used to measure the strain of an object. The most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.

All materials will deform when a stress or load is applied. Strain is a measure of the amount of deformation that occurs when an object is under stress. A strain gauge is an implement that is used to accurately measure this change in a material that is under load. Understanding the dimensional changes that occur when an object experiences strain is important in many mechanical design applications.

Elastic strain occurs when a material is subjected to a low level of stress. It will disappear after the stress is removed, and the material will return to its original state. At high levels of stress, a substance will deform to the point where it will not recover and return to its original dimensions. This is called plastic strain. A strain gauge can be used to determine when a material undergoes plastic strain and permanent deformation has occurred.

The metal-foil strain gauge is commonly used when a very small amount of strain and dimensional change occurs. This type works by measuring the change in electrical resistance that occurs when an electrically conductive material deforms. The metal-foil strain gauge typically consists of a series of very thin parallel lines of conductive metal applied to a thin foil. The foil is attached to a backing material that is electrically insulating, and will not conduct voltage or current.

Strain gauges are available for a variety of measurement applications. These are used to measure strain due to elongation caused by a pulling force, compression caused by a pushing force, or even pressure applied to a surface area by a weight or other load. Strain gauges are often used for experimental testing in a laboratory and can be permanently mounted to an object to allow ongoing measurement.
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