Multiple choice

A strain gauge has a resistance of 120 ohm and gauge factor of 2. This strain gauge is connected in series with a ballast resistance of 120 ohm across a 6 V supply. Determine the voltage sensitivity of the circuit when the gauge is subjected to pressure of 240 MN/m2. The modulus of elasticity is 200 GN/m2.

  1. 5 volts per unit strain

  2. 48 volts per unit strain

  3. 1.98 volts per unit strain

  4. 3 volts per unit strain
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D Correct answer
Explanation

Ballast resistance (Rb) = 120 ohm Strain gauge resistance (Rs) = 120 ohm Input voltage (Vi) = 6 V Gauge Factor = (G) = 2 Applied Stress (p)= 240 MN/ m2 Modulus of elasticity =(E) = 200 GN/m2 Strain= P/E(240 x 106)/(200 x 109) = 1.2 x 10-3 Voltage sensitivity of the circuit (sV) = ((Rb x Rs.)/(Rb+ Rs.)2) x G x Vi (120 x 120)/(120+120)2) x 2 x 6 = 3 volts per unit strain 

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