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

The bridge shown is supplied with V_s = 2 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 2 VR₁ = 800 ΩR₂ = 800 ΩR₃ = 60 ΩR₄ = 40 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 100 Ω, R₂ = 120 Ω and R₃ = 1000 Ω. Find the unknown resistor R₄.

R₁ = 100 ΩR₂ = 120 ΩR₃ = 1000 Ω

R₄ = Ω

3.Medium

A bridge with four 120 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads V_ab = 36.59 mV. Find the exact change ΔR of R₂.

V_s = 3 VR = 120 ΩV_ab = 36.59 mV

ΔR = Ω

4.Medium

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

V_s = 3 VR₁ = 120 ΩR₂ = 500 ΩR₃ = 40 ΩR₄ = 40 Ω

R_th = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2.12) is excited with 2.5 V. The largest strain to be measured is 200 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2.12ε_max = 200 µεV_FS = 2.5 V

G =

6.Hard

A quarter bridge with one active gauge (GF = 2.12) is excited with 5 V. Under load the output reads 3.18 mV. Find the strain ε in µε.

V_s = 5 VGF = 2.12V_o = 3.18 mV

ε = µε

Answer key

1. I_s = 21.25 mA
2. R₄ = 1200 Ω
3. ΔR = 6.001 Ω
4. R_th = 116.8 Ω
5. G = 9434
6. ε = 1200 µε

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