Question

An N-type semiconductor strain gage has a nominal resistance of $1000\Omega$ and gauge factor of -100. The resistance of the gauge, when compressive strain $100\mu m/m$ is applied, is

• A. $900\Omega$
• B. $990\Omega$
• C. $1010\Omega$
• D. $1100\Omega$

Answer 1

The correct option is C $1010\Omega$

$G_f=\frac{\Delta R|R}{ϵ}$

Given that,
$G_f=-100$

$R=1000\Omega$

$ϵ=-100\mu m/m=-100\times {10}^{-6}m/m$

$-100=\frac{\Delta R/1000}{-100\times {10}^{-6}}$

$\Delta R=10$

$\therefore$ Resistance of gauge
$=R+\Delta R=1000+10$
$=1010\Omega$

Note : It can be observed that for senicondoctor strain gauges, sensitivity is very high i.e, for 100 $\mu m/m$ strain, change in resistance is 10 $\Omega$.