A motion is sensed by a displacement detector, a current is fed to the coil to get back the pendulum mass to the original position.

This current will be proportional to the acceleration, that is converted to an output voltage.

The Servo type accelerometer is for the Earthquake Monitoring or measurements of micro tremor on the Civil Engineering Structures because of its higher sensitivity and stability or more accurate phase responses in the lower frequency range than those of other vibration transducers.