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
+−5 VR1​ = 40 ΩR2​ = 400 ΩR3​ = ?R4​ = 20 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 40 Ω, R₂ = 400 Ω and R₄ = 20 Ω. Find the setting R3.

R1 = 40 ΩR2 = 400 ΩR4 = 20 Ω
R3 = Ω
2.Easy
+−5 VR1​ = 800 ΩR2​ = 50 ΩR3​ = ?R4​ = 40 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 800 Ω, R₂ = 50 Ω and R₄ = 40 Ω. Find the setting R3.

R1 = 800 ΩR2 = 50 ΩR4 = 40 Ω
R3 = Ω
3.Medium
+−10 VR1​ = 300 ΩR2​ = 200 ΩR3​ = 400 ΩR4​ = 10 Ωab+−Rth​ = ?

Find the Thévenin resistance Rth of the bridge shown, seen from the output terminals a and b.

Vs = 10 VR1 = 300 ΩR2 = 200 ΩR3 = 400 ΩR4 = 10 Ω
Rth = Ω
4.Medium
+−5 V220 Ω220 Ω + ΔR220 Ω220 Ωab+−Vab​ = ?

A bridge has four 220 Ω arms and Vs = 5 V. The sensor R₂ increases by ΔR = 1.76 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 5 VR = 220 ΩΔR = 1.76 Ω
Vab = mV
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 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 2.5 VGF = 2.12εmax = 1000 µεVFS = 2.5 V
G =
6.Hard
+−2.5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−1.875 mV

A quarter bridge with one active gauge (GF = 2) is excited with 2.5 V. Under load the output reads 1.875 mV. Find the strain ε in µε.

Vs = 2.5 VGF = 2Vo = 1.875 mV
ε = µε

Answer key

  1. 1. R3 = 2 Ω
  2. 2. R3 = 640 Ω
  3. 3. Rth = 129.8 Ω
  4. 4. Vab = 10 mV
  5. 5. G = 1887
  6. 6. ε = 1500 µε

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