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 = 300 ΩR₂ = 50 ΩR₃ = 80 ΩR₄ = 60 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 = 20 ΩR₂ = 300 ΩR₃ = 100 ΩR₄ = 40 Ω

V_ab = V

3.Medium

A bridge has four 250 Ω arms and V_s = 10 V. The sensor R₂ increases by ΔR = 62.5 Ω. Find the exact output V_ab in mV.

V_s = 10 VR = 250 ΩΔR = 62.5 Ω

V_ab = mV

4.Medium

A 250 Ω strain gauge is one arm (R₂) of a bridge with four equal 250 Ω arms and an excitation of 6 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 6 VR = 250 Ω

P_g = mW

5.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter 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. I_s = 90 mA
2. V_ab = 9.777 V
3. V_ab = 555.6 mV
4. P_g = 36 mW
5. V_o = 1.845 mV
6. V_o = 18 mV

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