Strain Gauge Resistance Change
ΔR = R × GF × ε
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Formula
Description
A strain gauge changes resistance proportionally to the mechanical strain applied to it. The gauge factor (GF) is the sensitivity: the ratio of fractional resistance change to strain. Metal foil gauges have GF ≈ 2, meaning 1 microstrain (1 µε = 1 ppm elongation) causes a 2 ppm resistance change. For a 350Ω gauge at 1000 µε, ΔR is only 0.7Ω, which is why Wheatstone bridges and precision instrumentation amplifiers are required for measurement. Semiconductor strain gauges have GF of 100-200 but are more temperature-sensitive.
Variables
- ΔR — Resistance change (Ω)
- R — Nominal gauge resistance (Ω)
- GF — Gauge factor (dimensionless)
- ε — Mechanical strain in microstrain (µε)
Practical Notes
Standard gauge resistances: 120Ω, 350Ω, 1000Ω. Higher resistance reduces self-heating and lead wire errors. The strain value entered is in microstrain (µε) and is automatically scaled by 1e-6 internally. Temperature compensation is achieved using dummy gauges or self-compensating gauge alloys. Load cells use multiple strain gauges in a full Wheatstone bridge for maximum sensitivity.
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