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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 2 V.

V_s = 2 VR₁ = 500 ΩR₂ = 100 ΩR₃ = 250 ΩR₄ = 1000 Ω

V_ab = V

2.Easy

In the bridge shown, V_s = 6 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 = 6 VR₁ = 80 ΩR₂ = 400 ΩR₃ = 100 ΩR₄ = 40 Ω

V_a = V

3.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 2 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 2 VR₁ = 200 ΩR₂ = 100 ΩR₃ = 100 ΩR₄ = 600 ΩR_g = 50 Ω

I_g = µA

4.Medium

A 100 Ω strain gauge is one arm (R₂) of a bridge with four equal 100 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 = 100 Ω

P_g = mW

5.Hard

A quarter bridge (one active gauge, GF = 2.1) is excited with 5 V. The largest strain to be measured is 1200 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 5 VGF = 2.1ε_max = 1200 µεV_FS = 3.3 V

G =

6.Hard

A bridge with 1000 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.05ε = 200 µε

V_o = mV

Answer key

1. V_ab = −1.267 V
2. V_a = 5 V
3. I_g = −5176 µA
4. P_g = 10 mW
5. G = 1048
6. V_o = 1.025 mV

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