H. W. Sullivan Ltd. Ballistic Galvanometers (Pair), London, England. A matched pair of precision laboratory galvanometers designed for the detection and measurement of very small electrical currents or transient charge pulses. Ballistic galvanometers of this type were widely used in electrical standards laboratories and research work for measuring capacitor charge, magnetic flux changes, and inductance experiments. c.1920s–1940s.
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