Wheatstone bridge & strain gauges worksheet with answers

Free printable Wheatstone bridge & strain gauges worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

In the bridge shown, V_s = 2 V, R₁ = 60 Ω and R₂ = 40 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 60 ΩR₂ = 40 ΩR₃ = 300 ΩR₄ = 400 Ω

V_a = V

2.Easy

The bridge shown is supplied with V_s = 2 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 2 VR₁ = 80 ΩR₂ = 10 ΩR₃ = 40 ΩR₄ = 10 Ω

I_s = mA

3.Medium

A 250 Ω strain gauge is one arm (R₂) of a bridge with four equal 250 Ω arms and an excitation of 10 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 10 VR = 250 Ω

P_g = mW

4.Medium

A bridge has four 120 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 6 Ω. Find the exact output V_ab in mV.

V_s = 6 VR = 120 ΩΔR = 6 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.1 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.1ε = 200 µε

V_o = mV

6.Hard

A strain gauge (GF = 2) on a member with E = 70 GPa forms a quarter bridge excited with 10 V. The output reads 3.75 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2V_o = 3.75 mVE = 70 GPa

σ = MPa

Answer key

1. V_a = 0.8 V
2. I_s = 62.22 mA
3. P_g = 100 mW
4. V_ab = 73.17 mV
5. V_o = 0.63 mV
6. σ = 52.5 MPa

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