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 = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 80 ΩR₂ = 100 ΩR₃ = 800 ΩR₄ = 120 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 80 Ω, R₂ = 800 Ω and R₃ = 60 Ω. Find the unknown resistor R₄.

R₁ = 80 ΩR₂ = 800 ΩR₃ = 60 Ω

R₄ = Ω

3.Medium

A bridge with four 1000 Ω arms is supplied with 5 V. When the sensor R₂ changes, the output reads V_ab = 60.98 mV. Find the exact change ΔR of R₂.

V_s = 5 VR = 1000 ΩV_ab = 60.98 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 = 9 VR₁ = 20 ΩR₂ = 50 ΩR₃ = 40 ΩR₄ = 400 Ω

R_th = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 2.5 V. The largest strain to be measured is 1500 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 = 2.05ε_max = 1500 µεV_FS = 2.5 V

G =

6.Hard

A bridge with 350 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 1500 µε

V_o = mV

Answer key

1. I_s = 19.93 mA
2. R₄ = 600 Ω
3. ΔR = 50 Ω
4. R_th = 50.65 Ω
5. G = 1301
6. V_o = 1.875 mV

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