The multi-vibration galvanometer
P Rothwell · Journal of Scientific Instruments · 1925
A vibration galvanometer with a number of elements of Campbell type tuned in succession to cover a range of acoustical frequency is described. It is necessary to keep the tension of an element sufficiently large, in order to have only one mode of vibration within the range of frequency and to have greatest sensitivity and stability in tuning. Tuning, which must be principally dependent on length and thickness of suspension for a given coil, is carried out by means of an electrical oscillating circuit, adjustable in frequency. An improved design is described. These instruments are very insensitive to mechanical shock.