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 = 6 V.

V_s = 6 VR₁ = 300 ΩR₂ = 250 ΩR₃ = 50 ΩR₄ = 800 Ω

V_ab = V

2.Easy

The bridge shown is supplied with V_s = 12 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 12 VR₁ = 60 ΩR₂ = 200 ΩR₃ = 300 ΩR₄ = 10 Ω

I_s = mA

3.Medium

A bridge has four 350 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 2.8 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 3 VR = 350 ΩΔR = 2.8 Ω

V_ab = mV

4.Medium

A bridge has four 1000 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 1 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 15 VR = 1000 ΩΔR = 1 Ω

V_ab = mV

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output V_o under a load of 37.5 kg.

3 mV/VF_rated = 50 kgV_s = 10 VF = 37.5 kg

V_o = mV

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 2.12 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.12ε = 1000 µε

V_o = mV

Answer key

1. V_ab = −2.92 V
2. I_s = 84.86 mA
3. V_ab = 6 mV
4. V_ab = 3.75 mV
5. V_o = 22.5 mV
6. V_o = 1.325 mV

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