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 = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 1000 ΩR₂ = 200 ΩR₃ = 20 ΩR₄ = 200 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 12 V, R₁ = 250 Ω and R₂ = 1000 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 12 VR₁ = 250 ΩR₂ = 1000 ΩR₃ = 200 ΩR₄ = 60 Ω

V_a = V

3.Medium

A bridge has four 470 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 0.47 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 9 VR = 470 ΩΔR = 0.47 Ω

V_ab = mV

4.Medium

A bridge has four 150 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 0.6 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 150 ΩΔR = 0.6 Ω

V_ab = mV

5.Hard

A bridge with 120 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1200 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 1200 µε

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 5 V. The largest strain to be measured is 500 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 5 VGF = 2ε_max = 500 µεV_FS = 2.5 V

G =

Answer key

1. I_s = 16.14 mA
2. V_a = 9.6 V
3. V_ab = 2.25 mV
4. V_ab = 6 mV
5. V_o = 1.8 mV
6. G = 2000

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