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
+−3 VR1​ = 1000 ΩR2​ = 200 ΩR3​ = ?R4​ = 600 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 1000 Ω, R₂ = 200 Ω and R₄ = 600 Ω. Find the setting R3.

R1 = 1000 ΩR2 = 200 ΩR4 = 600 Ω
R3 = Ω
2.Easy
+−6 VR1​ = 600 ΩR2​ = 150 ΩR3​ = 250 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 600 Ω, R₂ = 150 Ω and R₃ = 250 Ω. Find the unknown resistor R4.

R1 = 600 ΩR2 = 150 ΩR3 = 250 Ω
R4 = Ω
3.Medium
+−6 V400 Ω400 Ω400 Ω400 Ωab+−

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 Ω arms and an excitation of 6 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 6 VR = 400 Ω
Pg = mW
4.Medium
+−3 V220 Ω220 Ω + ΔR220 Ω220 Ωab+−Vab​ = ?

A bridge has four 220 Ω arms and Vs = 3 V. The sensor R₂ increases by ΔR = 33 Ω. Find the exact output Vab in mV.

Vs = 3 VR = 220 ΩΔR = 33 Ω
Vab = mV
5.Hard
+−10 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 10 V. The largest strain to be measured is 250 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 10 VGF = 2εmax = 250 µεVFS = 5 V
G =
6.Hard
+−3 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 3 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 1200 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2ε = 1200 µε
Vo = mV

Answer key

  1. 1. R3 = 3000 Ω
  2. 2. R4 = 62.5 Ω
  3. 3. Pg = 22.5 mW
  4. 4. Vab = 104.7 mV
  5. 5. G = 4000
  6. 6. Vo = 7.2 mV

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