The range of a Monitor is measured from its installation point to where the majority of the water/ foam discharge falls. However, some standards/ practices measure the distance to the farthest point of the discharge. Range will be mentioned in the data sheet of the monitor.
The ‘effective range’ is not an official definition but gives the actual range of the monitor in real conditions (taking into consideration factors such as unfavourable wind conditions). For e.g. a monitor with a 60 M range would actually be installed at a distance between 35 to 45 M from the hazard, to cater for unfavourable wind conditions, and ensure effective performance.