A geophone is a device that converts ground movement (velocity) into voltage.

Geophones typically comprise a spring-mounted magnetic mass moving within a wire coil to generate an electrical signal. The response of a coil/magnet geophone is proportional to ground velocity.

Geophones for recording blasting vibration should be able to record from 0.1mm/sec to 300mm/sec and over a frequency range from 4.5 Hz to 250 Hz.

Geophones require annual calibration by an approved testing station (NATA) to ensure they continue to accurately record ground vibration.