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​ = 120 ΩR2​ = 120 ΩR3​ = 120 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 = 120 ΩR2 = 120 ΩR3 = 120 ΩR4 = 500 Ω
Is = mA
2.Easy
+−9 VR1​ = 300 ΩR2​ = 120 ΩR3​ = 150 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 300 Ω, R₂ = 120 Ω and R₃ = 150 Ω. Find the unknown resistor R4.

R1 = 300 ΩR2 = 120 ΩR3 = 150 Ω
R4 = Ω
3.Medium
+−9 V300 Ω300 Ω + ΔR300 Ω300 Ωab+−173.1 mV

A bridge with four 300 Ω arms is supplied with 9 V. When the sensor R₂ changes, the output reads Vab = 173.1 mV. Find the exact change ΔR of R₂.

Vs = 9 VR = 300 ΩVab = 173.1 mV
ΔR = Ω
4.Medium
+−9 V300 Ω300 Ω + ΔR300 Ω300 Ωab+−214.3 mV

A bridge with four 300 Ω arms is supplied with 9 V. When the sensor R₂ changes, the output reads Vab = 214.3 mV. Find the exact change ΔR of R₂.

Vs = 9 VR = 300 ΩVab = 214.3 mV
ΔR = Ω
5.Hard
+−2.5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2.12) is excited with 2.5 V. The largest strain to be measured is 1000 µε, and it must give 10 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 2.5 VGF = 2.12εmax = 1000 µεVFS = 10 V
G =
6.Hard
+−2.5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−1.575 mV

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 1.575 mV. Find the axial stress σ in MPa.

Vs = 2.5 VGF = 2.1Vo = 1.575 mVE = 200 GPa
σ = MPa

Answer key

  1. 1. Is = 69.35 mA
  2. 2. R4 = 60 Ω
  3. 3. ΔR = 24 Ω
  4. 4. ΔR = 30 Ω
  5. 5. G = 7547
  6. 6. σ = 240 MPa

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