A determination of the absolute ohm, using an improved self inductor
Harvey L. Curtis, Charles Moon, Chris M. Sparks · Journal of research of the National Bureau of Standards · 1938
A second determination of the value of the absolute ohm has been completed. The same method as that previously described has been followed. This required the computation of the inductance of a solenoid from its measured dimensions and the elect! ical measurement of the same inductance in terms of resistance and time. Refinements were made in many of the details of measurement. Two important improvements were introduced. A new inductor was constructed in which the wire was wound in a screw thread of uniform pitch cut in a glass tube. The error in the computed in(iuctance which resulted from the variations in pitch has been practicaUy eliminated, whereas in the previous inductors this introduced one of the largest uncertainties. The other improvement was in the alternatingcurrent bridge measurements, wher e the effect of the capacitance to earth of the inductor was evaluated.