A dual bridge for the measurement of self inductance in terms of resistance and time
Harvey L. Curtis, Leon W. Hartman · Journal of research of the National Bureau of Standards · 1940
A dual bridge for the measurement of self inductance in terms of resistance and time is described, its theory is developed, and eX'perimental results are given.The dual bridge consists of a primary bridge and a detector bridge, both of which are independently balanced for continuous current.The primary bridge has the inductance to be measured in one of its resistance arms and a source of unidirec-I tional pulsating current in its battery arm.In its galvanometer arm there is > connected, through a rectifying switch, the detector bridge which has an integrating galvanometer in one of its resistance arms and a battery as a source of current.The current from the battery is adjusted until its effect on the integrating galvanometer is equal and opposite to that of the pulseslof current from the primary bridge.The theory not only gives the formula for computing the inductance, but also a formula for determining the maximum number of pulses per second that may be employed with a given }set of bridge constants in order to obtain a desired accuracy.The experimental results show that the method can readily be used to measure inductances as large as 1 henry, with an accuracy of 1 part in 1,000.There are indications that results of much higher accuracy can be obtained.