Question

A strain gauge having a nominal resistance $120\Omega$ and a gauge factor of $2.1$. It is shunted by a resistance of $100k\Omega$, then the equivalent strain that will be indicated when tthe gauge is shunted is

• A. $1200\mu strain$
• B. $-9\mu strain$
• C. $300\mu strain$
• D. $-570\mu strain$

Answer 1

The correct option is D $-570\mu strain$

When the gauge is shunted the equivalent resistance of the strain gauge is given by


$R_{eq}=\frac{120\times 100\times 1000}{100000+120}=119.856\Omega$

$\text{Change in resistance}\Delta R=R_{eq}-R_G$

$=119.856-120=-0.144\Omega$

$G.F=\frac{\Delta R/R}{\epsilon }$

$\epsilon =\frac{\Delta R}{R\times G.F}=\frac{-0.144}{120\times 2.1}$

$=-570\times {10}^{-6}$

$=-570\mu strain$