With the Sencore PR57 supplying AC power to the Belkin 1000VA UPS, we adjusted the voltage from 120VAC up to 140VAC to simulate a spike in the utility power supply. When the Belkin Universal 1000VA UPS cuts itself off from the AC input and switches to its alternate source, we'll be monitoring what happens to the output voltage as the UPS strives to compensate in that split second.

With a computer running off the UPS power supply, we use a Digital Multimeter to measure the voltage levels, and more importantly, where the output voltage dips during the switching process. The switch from AC to battery power occurs rapidly, but not instantaneously... If the output voltage dips too low, for too long, it can cause instability in a sensitive powersuppy and disrupt the computer.

UPS Output Voltage & Variable Utility Supply (+/- 3%) Under-Voltage Trip Points: Over-Voltage Trip Point: Lowest Output Voltage: 50V 60V 70V 80V 90V 100V 110V 115V 120V 130V 140V Utility VAC Belkin 1000VA 102 102 102 102 107 117 127 115 120 128 98 122 110, 90 135 98 Powerware 5125 120 120 120 120 114 112 108 115 120 114 124 124 110, 95, 85 127 107 No UPS, idle. - - - 80 90 100 109 115 120 130 - 123 -

Test Observations: The Belkin Universal 1000VA UPS output voltage fluctuated during the 90V utility undervoltage trip point from between 102-117VAC as a mechanical relay moved the test load (computer) from one power circuit to another. The lowest we saw UPS output voltage reach was 98VAC, though only for a very brief moment during the change over from one source to the other.