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 = 15 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 15 VR₁ = 100 ΩR₂ = 60 ΩR₃ = 250 ΩR₄ = 120 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 2 V, R₁ = 80 Ω and R₂ = 20 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 80 ΩR₂ = 20 ΩR₃ = 600 ΩR₄ = 200 Ω

V_a = V

3.Medium

A bridge has four 350 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 0.875 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 9 VR = 350 ΩΔR = 0.875 Ω

V_ab = mV

4.Medium

A 120 Ω strain gauge is one arm (R₂) of a bridge with four equal 120 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 = 120 Ω

P_g = mW

5.Hard

A bridge with 350 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 800 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.05ε = 800 µε

V_o = mV

6.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 10 V. Under load the output reads 7.5 mV. Find the strain ε in µε.

V_s = 10 VGF = 2V_o = 7.5 mV

ε = µε

Answer key

1. I_s = 134.3 mA
2. V_a = 0.4 V
3. V_ab = 5.625 mV
4. P_g = 75 mW
5. V_o = 4.1 mV
6. ε = 1500 µε

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