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 = 2 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 2 VR₁ = 10 ΩR₂ = 20 ΩR₃ = 200 ΩR₄ = 50 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 5 V, R₁ = 60 Ω and R₂ = 400 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 5 VR₁ = 60 ΩR₂ = 400 ΩR₃ = 10 ΩR₄ = 1000 Ω

V_a = V

3.Medium

A 300 Ω strain gauge is one arm (R₂) of a bridge with four equal 300 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 = 300 Ω

P_g = mW

4.Medium

A bridge has four 220 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 0.44 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 3 VR = 220 ΩΔR = 0.44 Ω

V_ab = mV

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output V_o under a load of 30 kg.

2.5 mV/VF_rated = 50 kgV_s = 10 VF = 30 kg

V_o = mV

6.Hard

A bridge with 350 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 600 µε

V_o = mV

Answer key

1. I_s = 74.67 mA
2. V_a = 4.348 V
3. P_g = 30 mW
4. V_ab = 1.5 mV
5. V_o = 15 mV
6. V_o = 0.9 mV

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