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​ = 200 ΩR2​ = 40 ΩR3​ = 20 ΩR4​ = 150 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 12 V.

Vs = 12 VR1 = 200 ΩR2 = 40 ΩR3 = 20 ΩR4 = 150 Ω
Vab = V
2.Easy
+−6 VR1​ = 150 ΩR2​ = 20 ΩR3​ = ?R4​ = 400 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 150 Ω, R₂ = 20 Ω and R₄ = 400 Ω. Find the setting R3.

R1 = 150 ΩR2 = 20 ΩR4 = 400 Ω
R3 = Ω
3.Medium
+−2 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 2 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 2 VR = 120 Ω
Pg = mW
4.Medium
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vab​ = ?

A bridge has four 350 Ω arms and Vs = 3 V. The sensor R₂ increases by ΔR = 2.8 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 3 VR = 350 ΩΔR = 2.8 Ω
Vab = mV
5.Hard
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 3 V. The largest strain to be measured is 1200 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 3 VGF = 2εmax = 1200 µεVFS = 3.3 V
G =
6.Hard
+−10 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2.1) is excited with 10 V. The largest strain to be measured is 250 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 10 VGF = 2.1εmax = 250 µεVFS = 2.5 V
G =

Answer key

  1. 1. Vab = −8.588 V
  2. 2. R3 = 3000 Ω
  3. 3. Pg = 8.333 mW
  4. 4. Vab = 6 mV
  5. 5. G = 1833
  6. 6. G = 1905

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