Patent ID: 9063249
Filing Date: 2015-06-23
Classification: G01V,H04B

Abstract:
1. A system for measuring a time offset of an acoustic sensor node relative to a reference time, the system comprising: an acoustic communications unit arranged to transmit a first acoustic probe signal to the acoustic sensor node; a processing resource operably coupled to the acoustic communications unit and arranged to record a transmission time of the first signal, the transmission time being relative to the reference time; wherein the acoustic sensor node is arranged to receive the first signal and to transmit a second acoustic reply signal to the acoustic communications unit after a predetermined time delay, the second signal including time data indicative of a current internal time of the acoustic sensor node during the predetermined time delay; and the acoustic communications unit is arranged to receive the second signal, the processing resource recording a receive time at which the second signal is received, the receive time also being relative to the reference time, and to calculate the combined time of flight of the first and second signals, and using the combined time of flight and the predetermined time delay to calculate the time offset between the current internal time of the sensor node and the reference time.