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How should I choose a UPS?
by Nyal MellorApril 08, 2013
The major considerations are:
How much power does the UPS need to supply?
In the event of a power outage the only devices you really need to keep on battery power are pieces of sensitive equipment such as projectors, computers and the like. To size the UPS add up the power consumption, in watts, of these devices. This information can be found in the manual, from your equipment manufacturer or by using a power meter. You should then compare this figure to the UPS rated capacity, which is also given in watts. We recommend specifying a UPS that is rated for 150% of the load you need since most manufacturer's quoted battery run time and THD performance is based on 50-75% load.
How long does the UPS need to supply power for?
A UPS is intended to allow for proper shutdown of connected equipment, not continuous operation. If you want to operate your system in an extended blackout then the solution you need is a generator not a UPS. 10-15 minutes of run time is generally sufficient.
Additional considerations:
Does the UPS output a true or stepped sine wave?
Most UPS systems do not output a true smooth sine wave but something that looks more like a set of steps. A stepped sine wave is, by its very nature, high in THD. Switch mode power supplies found in computers and projectors are fine running on stepped sine waves but our recommendation is that all audio gear using linear power supplies (which is nearly all of it) is fed a true sine wave output with distortion below 2%. An important thing to note is that the UPS technology has nothing to do with what the output looks like. It is generally true that most standby devices output a square wave, most line interactive output a stepped sine and most online dual conversion ones output a true sine wave but this is not a rule just a reflection on the typical products available from most manufacturers.
Nyal Mellor
Author