Device for Matching a Galvanometer or dc Indicator to Its Associated Circuit
T. M. Dauphinee · Review of Scientific Instruments · 1958
A simple apparatus for matching a dc galvanometer to any circuit resistance is described. Impedance matching is achieved by use of a chopper and transformer circuit which permits near optimum use of the available power. The circuit can also be used to expand the range of a microammeter or potentiometer recorder for use with thermocouples. Recorder scale expansions by factors of 10 to 30 have been achieved on low resistance thermocouples permitting readings to ±0.05 to 0.02°C with a standard 10 mv instrument.