Independently of the Davicom’s settings, the DVLD’s internal circuit is always operating and actively listening for the electromagnetic signature of lightning strikes. It can detect both cloudto-ground and cloud-to-cloud strikes. If the hardware-based averaging and distance estimation algorithm detects a strike at a distance that is closer than about 40 km, it will output this number to the Davicom unit for further action. Actually, the Davicom unit reads the data out of the DVLD once every second. It is important to note that this averaging and distance estimation takes place on a 17 minute cycle in the hardware. This means that once a strike has been detected (and the information sent to the Davicom), the DVLD won’t send a return to normal reading until 17 minutes later (if no other lightning strikes are detected).
If the storm keeps approaching however, the DVLD will continue to update its output to the Davicom with shorter and shorter distances.
This is where the “Distance Trigger” setting on the Davicom comes into play. Although the DVLD is continuously monitoring and outputting any distances to approaching lightning activity, a user can decide to ignore any strikes that occur too far away by setting the Davicom’s distance threshold to a smaller distance. The closer this distance is to the site, the fewer nuisance alarms will be caused by tangentially moving storms. On the other hand it is up to the user to decide how comfortable he is with the risk that a fast-approaching storm could zoom-in to his site with little or no forewarning. A display of 63 km indicates that no lightning has been detected.