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 = 12 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 12 VR₁ = 800 ΩR₂ = 400 ΩR₃ = 40 ΩR₄ = 80 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 9 V, R₁ = 200 Ω and R₂ = 80 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 9 VR₁ = 200 ΩR₂ = 80 ΩR₃ = 500 ΩR₄ = 500 Ω

V_a = V

3.Medium

A 120 Ω strain gauge is one arm (R₂) of a bridge with four equal 120 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 120 Ω

P_g = mW

4.Medium

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

V_s = 9 VR₁ = 80 ΩR₂ = 100 ΩR₃ = 200 ΩR₄ = 200 Ω

R_th = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 10 V. The largest strain to be measured is 500 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 10 VGF = 2ε_max = 500 µεV_FS = 3.3 V

G =

6.Hard

A 120 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.0615 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.05ΔR = 0.0615 Ω

ε = µε

Answer key

1. I_s = 110 mA
2. V_a = 2.571 V
3. P_g = 8.333 mW
4. R_th = 144.4 Ω
5. G = 1320
6. ε = 250 µε

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