This Rubicon galvanometer was used to detect and measure very small currents before the advent of digital ammeters. The earliest versions of galvanometers usually had a mirror attached to a fiber and the angular deflection served to show both polarity and magnitude of the current. This unit, standing about 15 cm in height, showed the deflection of a small spring coil against a calibrated scale. The right-hand photo shows the two terminals where the circuit wires were connected and a larger central knob that was used to zero the meter. This galvanometer was built by the Rubicon Company of Philadelphia, USA. This company built a wide range of electrical measuring equipment.
