Noise and Ripple can easily be measured by an oscilloscope. These show how much voltage fluctuation there is on a particular rail. We tested the rail stability of the 3.3 volt, 5 volt and 12 volt rails using an identical time and millivolt scale for all graphs. millivolt ripple is measured by the peak to peak size of the voltage curve.
Sample Ripple Graph
The latest ATX 12 volt version 2.3 specifications state that ripple from peak to peak must be no higher than 50 millivolts for the 3.3 volt and 5 volt rails, while the 12 volt rail is allowed up to 120 millivolts peak to peak to stay within specifications. Millivolt figures are stated to the closest increment of 5 given their variability.
Load (%) | 3.3V Ripple | 5V Ripple | 12V Ripple |
20 | 8.2 | 7.4 | 11.8 |
40 | 9.4 | 8.8 | 13.4 |
60 | 12.6 | 10.6 | 19.2 |
80 | 16.4 | 17.2 | 24.4 |
100 | 18.6 | 20.2 | 33.6 |
12 volt performance is absolutely top-draw, less than 35mV peak to peak ripple at full load is well under ATX spec of 150mV. The 3.3 and 5 volt performance is good but it could be stronger. As expected the Teapo filtering capacitors for the secondary side let this unit down a little. Top PSUs using ALL Japanese capacitors will typically run with 7.5-12.5mV ripple on the 3.3 and 5 volt rails, not up to 20mV. For all intents and purposes this doesn’t make much difference though.
3.3 volt @ 100%
5 volt @ 100%
12 volt @ 100%
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