Data is acquired and stored in a cyclic function on disk memory until a ring buffer trigger event is registered. A triggered event could be manual, timed or a channel alarm amplitude level crossing or skyline alarm. Then a predefineable posttrigger timer is decremented to zero and then stops the data storage. Thus the ringbuffer can be divided in pre- and posttrigger domains. Data recorded before the start of the posttrigger counter is in the pretrigger domain, data recorded after the start of the counter is in the posttrigger domain. The size (time) of the pre- and posttrigger domain can be set by the user from 1s to 1h each. Ring buffer trigger events can be generated manually or when signal alarms are detected.