Edward Simmons and Arthur Ruge invented the strain gauge in 1938; it is an object that is used to measure the strain of an object. There are many different types of strain gauges but the most common and simplest form is made up of an insulating backing which holds a metallic foil. When it becomes deformed by pressure, the electrical resistance changes; a wheatstone bridge is used to measure the resistance change. The electrical resistance is thus comparable to the strain (RDP, n.d.). A strain gauge makes its measurements by using the property of electrical conductance, and as stated previously the amount of applied stress can be deduced. The conductor is arranged in a zig-zag pattern and when stretched the resistance increases. To calculate the gauge factor the following equation can be used were (delta) R is the change in resistance; RG is the resistance of the gauge before it is deformed, and is the strain (Wikipedia, 2013).
Temperature has various effects on the strain gauges, such as increases in temperature will lead to expansion which can put stress on the gauge, and increase strain. Newer techniques, such as the use of constantan alloy have been used to counteract the effects of temperature such that they do not increase strain. Gauge’s that are not self-temperature- compensated can still be used by the addition of a dummy gauge.
Strain gauge’s are used in the practical sense to make pressure sensors. Civil engineers use mechanical types of strain gauges to measure the movements of buildings, foundations, and other sorts of structures. Different types of strain gauges exist for other methods. For example semiconductor gauges are used for measurements of small strain. Blood flow and tissue swelling also used a variant of strain gauges known as mercury-in rubber strain gauges (Wikipedia, 2013).
Works Cited
Anon, 2013. Strain Gauge. (Online) Available at: http://en.wikipedia.org/wiki/Strain_gauge (accessed on July 30,2013)
RDP group, n.d. How it works- strain gauge loading. (Online) Available at: http://www.rdpe.com/uk/hiw-sglc.htm (accessed on July 30, 2013)
