Question

Two electrical strain gauges are bonded to a duralumin cantilever as shown in below figure (a) and are connected in a bridge circuit as shown in figure (b). Each gauge has a resistance of $100\Omega$ and a gauge factor of $\mathrm{2.1.}$ The resistance of other two arms of the bridge are also $100\Omega$ each. The input voltage is $4V$ and the modulus of elasticity for duralumin is $70GN/m^2$. The output of the circuit $\left(V_0\right)$ when a stress of $200MN/m^2$ is applied to the cantilever is ___ $mV.$

• A. $1.2mV$
• B. $120mV$
• C. $12V$
• D. $12mV$

Answer 1

The correct option is D $12mV$

The arrangement shown in the figure is half bridge arrangement,

$\therefore V_0=\frac{G_f.ϵ}{2}{V}_s=\frac{2.1\times 200\times {10}^6}{70\times {10}^9}\times \frac{4}{2}$

$\therefore V_0=12mV$