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
+−9 VR1​ = 50 ΩR2​ = 200 ΩR3​ = ?R4​ = 1000 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 50 Ω, R₂ = 200 Ω and R₄ = 1000 Ω. Find the setting R3.

R1 = 50 ΩR2 = 200 ΩR4 = 1000 Ω
R3 = Ω
2.Easy
+−3 VR1​ = 60 ΩR2​ = 40 ΩR3​ = ?R4​ = 60 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 60 Ω, R₂ = 40 Ω and R₄ = 60 Ω. Find the setting R3.

R1 = 60 ΩR2 = 40 ΩR4 = 60 Ω
R3 = Ω
3.Medium
+−2 V330 Ω330 Ω330 Ω330 Ωab+−

A 330 Ω strain gauge is one arm (R₂) of a bridge with four equal 330 Ω arms and an excitation of 2 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 2 VR = 330 Ω
Pg = mW
4.Medium
+−3 V400 Ω400 Ω + ΔR400 Ω400 Ωab+−Vab​ = ?

A bridge has four 400 Ω arms and Vs = 3 V. The sensor R₂ increases by ΔR = 0.4 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 3 VR = 400 ΩΔR = 0.4 Ω
Vab = mV
5.Hard
+−5 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 500 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2ε = 500 µε
Vo = mV
6.Hard
+−10 V1000 Ω − ΔR1000 Ω + ΔR1000 Ω + ΔR1000 Ω − ΔRab+−Vo​ = ?

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 200 kg. It is excited with 10 V. Find its output Vo under a load of 40 kg.

2 mV/VFrated = 200 kgVs = 10 VF = 40 kg
Vo = mV

Answer key

  1. 1. R3 = 250 Ω
  2. 2. R3 = 90 Ω
  3. 3. Pg = 3.03 mW
  4. 4. Vab = 0.75 mV
  5. 5. Vo = 2.5 mV
  6. 6. Vo = 4 mV

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