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 = 250 ΩR₂ = 40 ΩR₃ = 20 ΩR₄ = 800 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 3 V, R₁ = 80 Ω and R₂ = 400 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 3 VR₁ = 80 ΩR₂ = 400 ΩR₃ = 250 ΩR₄ = 100 Ω

V_a = V

3.Medium

A bridge has four 400 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 1 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 400 ΩΔR = 1 Ω

V_ab = mV

4.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 15 VR₁ = 60 ΩR₂ = 50 ΩR₃ = 600 ΩR₄ = 50 Ω

R_th = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2.12) is excited with 5 V. The largest strain to be measured is 1500 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 = 2.12ε_max = 1500 µεV_FS = 2.5 V

G =

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 1000 kg. It is excited with 5 V. Find its output V_o under a load of 750 kg.

2 mV/VF_rated = 1000 kgV_s = 5 VF = 750 kg

V_o = mV

Answer key

1. I_s = 14 mA
2. V_a = 2.5 V
3. V_ab = 3.75 mV
4. R_th = 73.43 Ω
5. G = 628.9
6. V_o = 7.5 mV

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