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 = 50 ΩR₂ = 20 ΩR₃ = 100 ΩR₄ = 200 Ω

V_ab = V

2.Easy

The bridge shown is supplied with V_s = 2 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 2 VR₁ = 60 ΩR₂ = 80 ΩR₃ = 600 ΩR₄ = 600 Ω

I_s = mA

3.Medium

A bridge with four 150 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads V_ab = 146.3 mV. Find the exact change ΔR of R₂.

V_s = 12 VR = 150 ΩV_ab = 146.3 mV

ΔR = Ω

4.Medium

A bridge has four 220 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 1.1 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 220 ΩΔR = 1.1 Ω

V_ab = mV

5.Hard

A strain gauge (GF = 2.1) on a member with E = 210 GPa forms a quarter bridge excited with 5 V. The output reads 3.15 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2.1V_o = 3.15 mVE = 210 GPa

σ = MPa

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 50 kg. It is excited with 12 V. Find its output V_o under a load of 40 kg.

1.5 mV/VF_rated = 50 kgV_s = 12 VF = 40 kg

V_o = mV

Answer key

1. V_ab = −5.714 V
2. I_s = 15.95 mA
3. ΔR = 7.5 Ω
4. V_ab = 7.5 mV
5. σ = 252 MPa
6. V_o = 14.4 mV

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