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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 15 V.

V_s = 15 VR₁ = 250 ΩR₂ = 50 ΩR₃ = 400 ΩR₄ = 800 Ω

V_ab = V

2.Easy

In a slide-wire (metre) bridge a known 20 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 75 cm from the left end A of the 100 cm wire. Find R_x.

R = 20 Ωl = 75 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 250 Ω arms and V_s = 12 V. The sensor R₂ increases by ΔR = 0.25 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 12 VR = 250 ΩΔR = 0.25 Ω

V_ab = mV

4.Medium

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

V_s = 6 VR₁ = 60 ΩR₂ = 300 ΩR₃ = 800 ΩR₄ = 300 Ω

R_th = Ω

5.Hard

A bridge with 350 Ω arms is excited with 5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 250 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2ε = 250 µε

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 3 V. The largest strain to be measured is 600 µε, and it must give 10 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 3 VGF = 2ε_max = 600 µεV_FS = 10 V

G =

Answer key

1. V_ab = −7.5 V
2. R_x = 6.667 Ω
3. V_ab = 3 mV
4. R_th = 268.2 Ω
5. V_o = 2.5 mV
6. G = 11111

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