At 100 km/h a vehicle will travel 27.8 cm per 100 Hz VBOX sample. That means we have to oversample the brake trigger in order to work out exactly when the brake trigger actually occurred. If we know when this event occurred then we can work out how far the vehicle travelled before the next sample.
The brake trigger is sampled at a much higher frequency than the GPS signals, and this parameter is called the ‘Trigger Event Time’. During data processing, this trigger event time is used to ensure the stopping distance is as accurate as possible.
On a VBOXIII/3i the trigger event time is directly stored as a time.
On a VBOXII the trigger event time is not time but the counter number, which will be from 0 - 11520.
VBOX Tools, VBOX Test Suite and the Multifunction display automatically pick up the trigger event time and use this in any calculation of braking
distance. At the same time, the latency of the VBOX is taken into account to remove any additional distance caused by processing delays.