Question

A single strain gauge of gauge factor $2$ is used in a wheatstone bridge in a quarter bridge arrangement where each resistance is $120\Omega$. If the bridge exciting voltage is $10cos1000tV$ and the gauge is subjected to sinusoidally varying strain of $500\mu m/m$ peak value and a frequency of $20Hz$. Then the equation for the output voltage as observed on a CRO (assuming infinite impedance for the CRO) is

• A. $0$
• B. $2.5cos1000t.sin40\pi tmV$
• C. $5cos1000t.sin40\pi tmV$
• D. $10cos1000t.sin40\pi tmV$

Answer 1

The correct option is B $2.5cos1000t.sin40\pi tmV$

$\because \text{Excitation voltage}$

$V_s=10cos1000tV$

$G.f=2$

$\text{Strain applied}\left(ϵ\right)=500sin(2\pi \times 2t)\mu m/m$

$\text{For quarter bridge arrangement}$

$V_0=\frac{V_{\epsilon }}{4}\times G.f\times ϵ$

$=\frac{10cos1000t\times 2\times 500sin40\pi t\times {10}^{-6}}{4}$

$=2.5cos1000tsin40\pi tmV$