DC bridge resistance resolution ($\delta R_1\simeq \delta V(R_1+R_2{)}^2/(V_s{R}_2)$)

With other arms fixed and a high-input-resistance detector, the DC midpoint difference has derivative $-V_s{R}_2/(R_1+R_2{)}^2$ with respect to $R_1$. Dividing a small detectable voltage change by its magnitude gives the local resistance resolution. Calibration, source stability, thermal drift and detector loading contribute separately to total measurement uncertainty. Detector sensitivity alone is not a complete accuracy claim.