What would be measured on a Galvanometer?
Thermo galvanometer of a resistance which is heated by the current to be measured, the heat from the resistance falling on the thermo-junction of a Boys radio-micrometer. The rise in temperature of the lower junction of the thermo-couple produces a current in the loop which is deflected by the magnetic field against the torsion of the quartz fibre. Thermo galvanometer The thermo-galvanometer is an instrument for measuring small electric currents. It was invented by William Duddell about 1900. The following is a description of the instrument taken from a trade catalog of Cambridge Scientific Instrument Company dated 1905: For a long time
Vibration galvanometer spring. The vibration galvanometer is used for detecting alternating currents in the frequency of its natural resonance. Most common application is as a null indicating instrument in AC bridge circuits and current comparators. The sharp resonance of the vibration galvanometer makes it very sensitive to changes in the measured current frequency and it can be used as an accurate tuning device. The frequency-sensitive behaviour of the galvanometer allows their use as a crude frequency meter, commonly used for adjusting the speed of AC generator sets. The galvanometer is constructed as a number of moving-iron galvanometers, sharing the same excitation coil.