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

The bridge shown is supplied with V_s = 10 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 10 VR₁ = 120 ΩR₂ = 40 ΩR₃ = 500 ΩR₄ = 80 Ω

I_s = mA

2.Easy

The bridge shown is supplied with V_s = 15 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 15 VR₁ = 120 ΩR₂ = 50 ΩR₃ = 500 ΩR₄ = 50 Ω

I_s = mA

3.Medium

A bridge has four 1000 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 1 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 1000 ΩΔR = 1 Ω

V_ab = mV

4.Medium

A bridge has four 400 Ω arms and V_s = 12 V. The sensor R₂ increases by ΔR = 32 Ω. Find the exact output V_ab in mV.

V_s = 12 VR = 400 ΩΔR = 32 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 2.5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 750 µε

V_o = mV

6.Hard

A strain gauge (GF = 2.1) on a member with E = 200 GPa forms a quarter bridge excited with 2.5 V. The output reads 0.328 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2.1V_o = 0.328 mVE = 200 GPa

σ = MPa

Answer key

1. I_s = 79.74 mA
2. I_s = 115.5 mA
3. V_ab = 1.5 mV
4. V_ab = 230.8 mV
5. V_o = 3.75 mV
6. σ = 49.98 MPa

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