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 by adjusting R₃. R₁ = 60 Ω, R₂ = 600 Ω and R₄ = 300 Ω. Find the setting R₃.

R₁ = 60 ΩR₂ = 600 ΩR₄ = 300 Ω

R₃ = Ω

2.Easy

The bridge shown is supplied with V_s = 5 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 5 VR₁ = 100 ΩR₂ = 100 ΩR₃ = 50 ΩR₄ = 300 Ω

I_s = mA

3.Medium

A bridge has four 500 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 1.25 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 2 VR = 500 ΩΔR = 1.25 Ω

V_ab = mV

4.Medium

A bridge with four 400 Ω arms is supplied with 9 V. When the sensor R₂ changes, the output reads V_ab = 109.8 mV. Find the exact change ΔR of R₂.

V_s = 9 VR = 400 ΩV_ab = 109.8 mV

ΔR = Ω

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 200 kg. It is excited with 12 V. Find its output V_o under a load of 80 kg.

2 mV/VF_rated = 200 kgV_s = 12 VF = 80 kg

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 400 µε, and it must give 10 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2ε_max = 400 µεV_FS = 10 V

G =

Answer key

1. R₃ = 30 Ω
2. I_s = 39.29 mA
3. V_ab = 1.25 mV
4. ΔR = 20 Ω
5. V_o = 9.6 mV
6. G = 20000

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