Method for Measurement of Small Direct Currents
by E.J. Harris
1947

This apparatus was described (named) in the Allied CIOS XXX-37 report
“Hisentroll and Hisenvert”.
(It is not clear to me, whether this is a German or an English designation)
It could measure down in to the 10^-15 regions.

Based upon a paper in: Rev. Sci. Instr. 1946, 17, 194

Both papers are based on specific German Scientific work commenced at the
Ernst Orlich Institute
of Danzig (now Gedansk), prior to 1944.

Its advantage was, that it did not utilized galvanometer techniques, which are, from its nature, very sensible to mechanical vibrations. Which latter devices had, to attain its optimal sensitivity, to be employed in bridge circuits as a “null indicator”. Consequently, not providing instantly current or voltage information (reading)

A mechanical precision chopper combined with a resonant step-up transformer, placed in the frond-end of the circuitry, allowed, electronically, unprecedented DC amplifications.

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