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 Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 100 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 200 ΩR₂ = 100 ΩR₃ = 600 Ω

R₄ = Ω

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 6 V.

V_s = 6 VR₁ = 10 ΩR₂ = 1000 ΩR₃ = 800 ΩR₄ = 300 Ω

V_ab = V

3.Medium

A bridge with four 500 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads V_ab = 38.46 mV. Find the exact change ΔR of R₂.

V_s = 2 VR = 500 ΩV_ab = 38.46 mV

ΔR = Ω

4.Medium

A bridge with four 200 Ω arms is supplied with 5 V. When the sensor R₂ changes, the output reads V_ab = 119 mV. Find the exact change ΔR of R₂.

V_s = 5 VR = 200 ΩV_ab = 119 mV

ΔR = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 800 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2ε_max = 800 µεV_FS = 5 V

G =

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 500 kg. It is excited with 5 V. Find its output V_o under a load of 125 kg.

1 mV/VF_rated = 500 kgV_s = 5 VF = 125 kg

V_o = mV

Answer key

1. R₄ = 300 Ω
2. V_ab = 4.304 V
3. ΔR = 40 Ω
4. ΔR = 20 Ω
5. G = 5000
6. V_o = 1.25 mV

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