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 = 100 ΩR₂ = 400 ΩR₃ = 120 ΩR₄ = 20 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 120 Ω, R₂ = 40 Ω and R₄ = 400 Ω. Find the setting R₃.

R₁ = 120 ΩR₂ = 40 ΩR₄ = 400 Ω

R₃ = Ω

3.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 500 Ω

P_g = mW

4.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 3 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 3 VR₁ = 60 ΩR₂ = 800 ΩR₃ = 60 ΩR₄ = 80 ΩR_g = 500 Ω

I_g = µA

5.Hard

A bridge with 120 Ω arms is excited with 2.5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.1 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.1ε = 600 µε

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 10 V. The largest strain to be measured is 200 µε, and it must give 10 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 10 VGF = 2.05ε_max = 200 µεV_FS = 10 V

G =

Answer key

1. I_s = 109.7 mA
2. R₃ = 1200 Ω
3. P_g = 4.5 mW
4. I_g = 1824 µA
5. V_o = 3.15 mV
6. G = 9756

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