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​ = 250 ΩR2​ = 200 ΩR3​ = ?R4​ = 1000 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 250 Ω, R₂ = 200 Ω and R₄ = 1000 Ω. Find the setting R3.

R1 = 250 ΩR2 = 200 ΩR4 = 1000 Ω
R3 = Ω
2.Easy
+−9 VR1​ = 20 ΩR2​ = 250 ΩR3​ = 40 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 250 Ω and R₃ = 40 Ω. Find the unknown resistor R4.

R1 = 20 ΩR2 = 250 ΩR3 = 40 Ω
R4 = Ω
3.Medium
+−10 V120 Ω120 Ω120 Ω120 Ωab+−

A 120 Ω strain gauge is one arm (R₂) of a bridge with four equal 120 Ω arms and an excitation of 10 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 10 VR = 120 Ω
Pg = mW
4.Medium
+−2 V250 Ω250 Ω + ΔR250 Ω250 Ωab+−9.9 mV

A bridge with four 250 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads Vab = 9.9 mV. Find the exact change ΔR of R₂.

Vs = 2 VR = 250 ΩVab = 9.9 mV
ΔR = Ω
5.Hard
+−10 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 750 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.05ε = 750 µε
Vo = mV
6.Hard
+−5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 5 V. The largest strain to be measured is 500 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 5 VGF = 2εmax = 500 µεVFS = 5 V
G =

Answer key

  1. 1. R3 = 1250 Ω
  2. 2. R4 = 500 Ω
  3. 3. Pg = 208.3 mW
  4. 4. ΔR = 4.999 Ω
  5. 5. Vo = 7.688 mV
  6. 6. G = 4000

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