Instrumentation Signal · Free Calculator
Strain Gauge and Wheatstone Bridge Calculator
Convert between strain, gauge resistance change and Wheatstone bridge output for quarter, half and full bridge strain gauge circuits.
Gauge factorµεQuarter bridgeFull bridge
Ω
µε
V
Resistance change ΔR0.35 Ω
ΔR ÷ R0.1 %
Bridge output2.499 mV
Bridge output0.2499 mV/V
How this result was calculated
- ΔR ÷ R = GF × ε = 2 × 0.0005
- Vout ≈ Vex × GF × ε × N ÷ 4 with N active gauges (quarter bridge exact form includes the nonlinearity term)
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Strain Gauge Formulas
GF = (ΔR ÷ R) ÷ ε
Quarter bridge: Vout = Vex × (GF ε ÷ 4) ÷ (1 + GF ε ÷ 2)
Half bridge (bending): Vout = Vex × GF ε ÷ 2 · Full bridge: Vout = Vex × GF ε
Quarter bridge: Vout = Vex × (GF ε ÷ 4) ÷ (1 + GF ε ÷ 2)
Half bridge (bending): Vout = Vex × GF ε ÷ 2 · Full bridge: Vout = Vex × GF ε
Worked example
500 µε on a 350 Ω gauge with GF 2.0 changes the resistance by 0.35 Ω. A quarter bridge at 10 V gives about 2.5 mV.
Key insight: bridge outputs are only millivolts, which is why load cells are specified in mV/V and need an instrumentation amplifier or dedicated bridge input.
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Frequently Asked Questions
What is a gauge factor?
The ratio of relative resistance change to strain; about 2.0 for metal foil gauges.
Why use a full bridge?
It gives four times the output of a quarter bridge and compensates for temperature.
What is a microstrain?
One millionth of a unit strain, 1 µε = 10⁻⁶ m/m.
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