L. Callegaro et V. D'Elia, Automatic compensation technique for alternating current metrology based on synchronous filtering, REV SCI INS, 69(12), 1998, pp. 4238-4241
In alternating current electrical metrology, the balancing procedure is the
act of reduction to zero of a measured terminal-pair voltage (or current),
accomplished via injection of a compensation voltage (current) in the circ
uit. An automatic compensation technique is described here: the terminal-pa
ir voltage is continuously sensed, by means of vector synchronous detection
, and the injected voltage is directly synthesized from the main circuit so
urce. An implementation of the compensation technique, realized with analog
electronics, permits compensation of audio frequency small voltages down t
o the nV range, with settling time in the order of milliseconds. (C) 1998 A
merican Institute of Physics. [S0034-6748(98)02812-3].