How The University of Nevada, Reno Keeps Its Lab Running When The Power Fails (Page 3)
Double conversion UPS systems for laboratory power protection are different than standard uninterrupted power supplies in the fact that double conversion (also referred to as online) units always have their batteries engaged. This means there is absolutely no switching time delay when battery power is required. In non-double conversion uninterruptible power supplies the switching delay normally ranges from 2-25 milliseconds. A small backup power switchover time is acceptable for most computer systems, but is not tolerated by sensitive laboratory instruments. Another benefit of most double conversion (online) uninterruptible power supplies is that they can use either grid/utility power or generator power as an input source.