Patent ID: 7353127

Claim:
A method of determining the frequency or period of a heartbeat, the method including the steps of: a) using a sensor to generate an electrical oscillatory signal representative of variation of the heartbeat, and using a computing apparatus to: b) observe the oscillatory signal by detecting the amplitude of the oscillatory signal; c) compute a first and a second moving average of the oscillatory signal, the first moving average having a first averaging time interval and the second moving average having a second averaging time interval longer than the first averaging time interval; d) determine the location in time of a plurality of crossing points, wherein a crossing point is a point of intersection between the first and second moving averages; e) define at least one measurement period as the interval between two crossing points; and f) determine the location in time of an absolute maximum or minimum of the oscillatory signal within the or each measurement period; and g) use the location in time of an absolute maximum from step f) to determine the frequency or period of the heartbeat.