Common Features: ■ Wide frequency range ■ Wide dynamic range ■ High input impedance ■ Wide application range ■ Small size Preamplifiers Types 2616, 2623, 2624, 2625 and 2626 When measuring vibration by means of an accelerometer it is necessary to incorporate a preamplifier between this and the measuring amplifier. The preamplifier is introduced in the measuring circuit for two reasons: 1) to amplify the relatively weak output signal from the accelerometer and 2) to transform the high output impedance of the accelerometer into a lower value. The signal from the piezoelectric accelerometer appears as a voltage across a capacitive impedance. This charge is proportional to the acceleration to which the accelerometer is exposed.