A Two-emf Method for the Comparison of Resistances
Harold J. Höge · Review of Scientific Instruments · 1954
A method of comparing resistances is described in which two sources of emf, each with an associated dropping resistor, are connected in series with two resistors to be compared, in such a way that the latter are not adjacent. The circuit may then be adjusted so that the potentials at the two ends of one of these resistances are equal to the potentials at the corresponding ends of the other resistance while both carry the same current. Convenient means of detecting and adjusting to this condition are described. The circuit may be used as an alternative to either the dc or the ac bridge. The method is suitable for work of either high or low accuracy. Its chief advantage over methods now in use is that it permits the continuous observation or recording of resistance without error due to uncontrolled changes in the resistances of the connecting leads. Readings are obtained directly, without the necessity of averaging or otherwise mathematically combining the results of more than one observation. If desired, more than two resistances to be compared may be included in the circuit, provided they are alternated with an equal number of emf's and associated dropping resistors.