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

In the bridge shown, V_s = 5 V, R₁ = 120 Ω and R₂ = 40 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 5 VR₁ = 120 ΩR₂ = 40 ΩR₃ = 20 ΩR₄ = 1000 Ω

V_a = V

2.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 = 40 ΩR₂ = 120 ΩR₃ = 20 ΩR₄ = 50 Ω

I_s = mA

3.Medium

A bridge with four 500 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads V_ab = 7.46 mV. Find the exact change ΔR of R₂.

V_s = 3 VR = 500 ΩV_ab = 7.46 mV

ΔR = Ω

4.Medium

A bridge has four 350 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 70 Ω. Find the exact output V_ab in mV.

V_s = 3 VR = 350 ΩΔR = 70 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 3 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.05 and the strain is 1200 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.05ε = 1200 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 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.

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

V_o = mV

Answer key

1. V_a = 1.25 V
2. I_s = 184.8 mA
3. ΔR = 4.998 Ω
4. V_ab = 136.4 mV
5. V_o = 7.38 mV
6. V_o = 18 mV

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