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 = 9 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 9 VR₁ = 20 ΩR₂ = 60 ΩR₃ = 50 ΩR₄ = 40 Ω

I_s = mA

2.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 = 200 ΩR₂ = 120 ΩR₃ = 120 ΩR₄ = 100 Ω

V_ab = V

3.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 = 600 ΩR₃ = 300 ΩR₄ = 150 Ω

R_th = Ω

4.Medium

A bridge has four 300 Ω arms and V_s = 12 V. The sensor R₂ increases by ΔR = 1.5 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 12 VR = 300 ΩΔR = 1.5 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 2.5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.1 and the strain is 250 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.1ε = 250 µε

V_o = mV

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 500 kg. It is excited with 10 V. Find its output V_o under a load of 300 kg.

1.5 mV/VF_rated = 500 kgV_s = 10 VF = 300 kg

V_o = mV

Answer key

1. I_s = 212.5 mA
2. V_ab = −1.193 V
3. R_th = 119.4 Ω
4. V_ab = 15 mV
5. V_o = 0.6563 mV
6. V_o = 9 mV

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