Reference resistors are affected by the heating of the resistor elemen
t caused by the measurement current. The effects of such loading are c
omplex and can change in magnitude as a function of the initial state
of the resistor and the external environment. This paper describes a m
ethod for determining relative load coefficients by using cryogenic cu
rrent comparator ratio measurements in a two-step scaling process. Pre
viously undiscovered loading effects are analyzed using a resistance e
lement made from copper, which has an easily measured change of resist
ance with temperature. The magnitude of loading effects in several typ
es of resistors are listed.