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 = 20 ΩR₂ = 300 ΩR₃ = 250 ΩR₄ = 60 Ω

I_s = mA

2.Easy

The bridge shown is supplied with V_s = 5 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 5 VR₁ = 60 ΩR₂ = 400 ΩR₃ = 1000 ΩR₄ = 500 Ω

I_s = mA

3.Medium

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

V_s = 15 VR₁ = 500 ΩR₂ = 60 ΩR₃ = 800 ΩR₄ = 300 Ω

R_th = Ω

4.Medium

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 Ω arms and an excitation of 10 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 10 VR = 400 Ω

P_g = mW

5.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 5 V. The largest strain to be measured is 800 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 = 2.05ε_max = 800 µεV_FS = 2.5 V

G =

6.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 2.5 V. Under load the output reads 1 mV. Find the strain ε in µε.

V_s = 2.5 VGF = 2V_o = 1 mV

ε = µε

Answer key

1. I_s = 57.16 mA
2. I_s = 14.2 mA
3. R_th = 271.8 Ω
4. P_g = 62.5 mW
5. G = 1220
6. ε = 800 µε

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