The resistances of 125 Ω strain gauge changes by 1 Ω for 4000 micro-strain. The gauge factor for strain gauge is

Concept:

The gauge factor is defined as the ratio of per unit change in resistance to per unit change in length.

Gauge factor \({G_f} = \frac{{{\rm{\Delta }}R/R}}{{{\rm{\Delta }}L/L}}\)

\(\frac{{{\rm{\Delta }}R}}{R} = {G_f}(\frac{{{\rm{\Delta }}L}}{L})= {G_f}~\varepsilon \)

Where ε = strain = ΔL/L

Calculation:

Given that, change in resistance (ΔR) = 1 Ω

Resistance (R) = 125 Ω

Micro strain (ε) = ΔL/L = 4000 μs

Gauge factor \( = \frac{{1/125}}{{4000 \times {{10}^{ - 6}}}} = 2\)