Gauge factor - wikipedia Gauge factor This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( December 2009 ) Gauge factor ( GF ) or strain factor of a strain gauge is the ratio of relative change in electrical resistance R, to the mechanical strain ε. The gauge factor is defined as : G F = Δ R R ε = Δ ρ ρ ε + 1 + 2 ν ( displaystyle GF = ( \frac ( \frac ( Delta R ) ( R ) ) ( \varepsilon ) ) = ( \frac ( \frac ( Delta \rho ) ( \rho ) ) ( \varepsilon ) ) + 1 + 2 \nu ) Or Gf = change in resistance / ( resistance * strain ) Where ε = strain = Δ L / L 0 ( displaystyle Delta L / L_ ( 0 ) ) Δ L ( displaystyle Delta L ) = absolute change in length L 0 ( displaystyle L_ ( 0 ) ) = original length ν = Poisson 's ratio ρ = Resistivity ΔR = change in strain gauge resistance R = unstrained resistance of strain gauge Piezoresistive effect It is a common misconception that the change in resistance of a strain gauge is based solely, or most heavily, on the geometric terms. This is true for some materials ( Δ ρ = 0 ( displaystyle Delta \rho = 0 ) ), and the gauge factor is simply : G F = 1 + 2 ν ( displaystyle GF = 1 + 2 \nu ) However, most commercial strain gauges utilise resistors made from materials that demonstrate a strong piezoresistive effect. The resistivity of these materials changes with strain, accounting for the first term of the defining equation above. In constantan strain gauges ( the most commercially popular ), the effect accounts for 20 % of the gauge factor, but in silicon gauges, the contribution of the piezoresistive term is much larger than the geometric terms. This can be seen in the general examples of strain gauges below : Material Gauge Factor Metal foil strain gauge 2 - 5 Thin - film metal ( e.g. constantan ) Single crystal silicon - 125 to + 200 Polysilicon ± 30 Thick - film resistors 100 p - type Ge 102 Effect of temperature The definition of the gauge factor does not rely on temperature, however the gauge factor only relates resistance to strain if there are no temperature effects. In practice, where changes in temperature or temperature gradients exist, the equation to derive resistance will have a temperature term. The total effect is : Δ R R = G F ε + α θ ( displaystyle ( \frac ( Delta R ) ( R ) ) = GF \varepsilon + alpha \theta ) Where α = temperature coefficient θ = temperature change Retrieved from `` https://en.wikipedia.org/w/index.php?title=Gauge_factor&oldid=791624981 '' Categories : Equations Hidden categories : Articles lacking sources from December 2009 All articles lacking sources Talk About Wikipedia فارسی Edit links This page was last edited on 21 July 2017, at 12 : 53. About Wikipedia

Question: what is the gauge factor of a strain gauge
Answer: the ratio of relative change in electrical resistance R, to the mechanical strain ε