The difficulty encountered in the past with any technique involving the use of an electrical stimulus has been that of obtaining a stimulating current which could at once be easily varied and accurately measured. In order to make it possible to vary the necessarily high voltage involved, an induction coil or transformer was usually used as the source of electrical current. Since these instruments have an alternating current output it is therefore difficult to obtain a meter capable of measuring the very small current that can be used as a stimulant. The ordinary A. C. meters are not adapted for measurement of very weak currents. In lieu of current measurement it has been customary to measure the applied E.M.F. Voltage, however, is an unreliable indicator of the energy put into the stimulus. The uncontrolled factor of variable skin and body resistance effects a corresponding variation in current, which is independent of the applied voltage.
Proceedings of the Iowa Academy of Science
©1927 Iowa Academy of Science, Inc.
Howells, Thomas H.
"An Electrical Stimulus Which Can Be Accurately Measured,"
Proceedings of the Iowa Academy of Science, 34(1), 305-306.
Available at: https://scholarworks.uni.edu/pias/vol34/iss1/102