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 = 120 Ω, R₂ = 200 Ω and R₄ = 50 Ω. Find the setting R₃.

R₁ = 120 ΩR₂ = 200 ΩR₄ = 50 Ω

R₃ = Ω

2.Easy

In the bridge shown, V_s = 12 V, R₁ = 50 Ω and R₂ = 400 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 12 VR₁ = 50 ΩR₂ = 400 ΩR₃ = 600 ΩR₄ = 10 Ω

V_a = V

3.Medium

A bridge has four 100 Ω arms and V_s = 5 V. The sensor R₂ increases by ΔR = 0.25 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 5 VR = 100 ΩΔR = 0.25 Ω

V_ab = mV

4.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 500 Ω

P_g = mW

5.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 3 V. The largest strain to be measured is 750 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 3 VGF = 2.05ε_max = 750 µεV_FS = 5 V

G =

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 500 kg. It is excited with 10 V. Find its output V_o under a load of 250 kg.

3 mV/VF_rated = 500 kgV_s = 10 VF = 250 kg

V_o = mV

Answer key

1. R₃ = 30 Ω
2. V_a = 10.67 V
3. V_ab = 3.125 mV
4. P_g = 12.5 mW
5. G = 4336
6. V_o = 15 mV

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