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
+−12 VR1​ = 800 ΩR2​ = 1000 ΩR3​ = 200 ΩR4​ = 500 Ωab+−

The bridge shown is supplied with Vs = 12 V and its output is open. Find the current Is drawn from the supply, in mA.

Vs = 12 VR1 = 800 ΩR2 = 1000 ΩR3 = 200 ΩR4 = 500 Ω
Is = mA
2.Easy
+−6 VR1​ = 1000 ΩR2​ = 60 ΩR3​ = 200 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 60 Ω and R₃ = 200 Ω. Find the unknown resistor R4.

R1 = 1000 ΩR2 = 60 ΩR3 = 200 Ω
R4 = Ω
3.Medium
+−3 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−14.85 mV

A bridge with four 1000 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads Vab = 14.85 mV. Find the exact change ΔR of R₂.

Vs = 3 VR = 1000 ΩVab = 14.85 mV
ΔR = Ω
4.Medium
+−10 V200 Ω200 Ω + ΔR200 Ω200 Ωab+−Vab​ = ?

A bridge has four 200 Ω arms and Vs = 10 V. The sensor R₂ increases by ΔR = 10 Ω. Find the exact output Vab in mV.

Vs = 10 VR = 200 ΩΔR = 10 Ω
Vab = mV
5.Hard
+−2.5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2.1) is excited with 2.5 V. The largest strain to be measured is 400 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 2.5 VGF = 2.1εmax = 400 µεVFS = 5 V
G =
6.Hard
+−2.5 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A bridge with 120 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 2.1 and the strain is 600 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.1ε = 600 µε
Vo = mV

Answer key

  1. 1. Is = 23.81 mA
  2. 2. R4 = 12 Ω
  3. 3. ΔR = 20 Ω
  4. 4. Vab = 122 mV
  5. 5. G = 9524
  6. 6. Vo = 3.15 mV

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