The AC-73 sensor package is a true electro-mechanical triaxial accelerometer designed for broadband earthquake monitoring and applications requiring highly sensitive and rugged sensors with minimum maintenance and a simple method for periodic testing.

The AC-73 accelerometer is based on a force balance servo accelerometer concept having a rugged mass suspension moving coil system. The large mass improves the signal to noise ratio. The magnetic system and capacitive position sensors offer symmetrical controls for the accurate electronic centring of the mass. At rest the accelerometer servo mechanism is in balance and no electrical output is generated. Acceleration of the AC-73 will result in an electrical output proportional to the current used to keep the mass centred. This accelerometer output signal is calibrated to “g” gravity so that the current scale factor of the AC-73 is in units of milliamps per g. Because of the symmetrical positioning system incorporated with the force balance servo accelerometer principle, the accelerometer can not arbitrarily change its scaling or drift out of calibration.