On the evaluation of measurements of small changes in electric resistance

The measurement of small changes in resistance, caused in metal wires by non-equilibrium point defects, meets with many difficulties caused inter alia by changes in temperature, instability of the voltage source and irreversible changes in the electric resistance due to the thermal treatment of the samples. In the first part of the paper, dealing with the d-c bridge method of measurement, the conditions under which the relations given in the literature can be used for calculating small changes in resistance are quantitatively determined on the basis of a detailed analysis of such relations. The second part describes a method of measurement permitting the elimination of irreversible changes in the resistance of thermally treated samples and relations are derived for calculating reversible changes.