GATE2013-26

Question

A strain gauge forms one arm of the bridge shown in the figure below and has a nominal resistance
without any load as $R_s$ = $300$ . Other bridge resistances are $R_1$ = $R_2$ = $R_3$ = $300$ . The maximum
permissible current through the strain gauge is $20$ $mA$. During certain measurement when the
bridge is excited by maximum permissible voltage and the strain gauge resistance is increased by
$1$% over the nominal value, the output voltage $V_0$ in $mV$ is

• A. $56.02$
• B. $40.83$
• C. $29.85$
• D. $10.02$

Answer 1

Voltage, Vin = (300+300)*20m

                      = 12v

Now, V _{0 =  6-((300/603)*12)}

                = 0.03v.   I.e., 30mV