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Ripple Measurements
To learn how we measure ripple, please click here.
The following table includes the ripple levels we measured on the EPF1200EWT's rails. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V and 5VSB).
| Test | 12V | 5V | 3.3V | 5VSB | Pass/Fail |
|---|---|---|---|---|---|
| 10% Load | 12.9mV | 4.9mV | 5.3mV | 4.0mV | Pass |
| 20% Load | 19.7mV | 6.0mV | 6.9mV | 5.6mV | Pass |
| 30% Load | 28.2mV | 6.7mV | 16.5mV | 8.6mV | Pass |
| 40% Load | 32.9mV | 7.7mV | 18.3mV | 10.5mV | Pass |
| 50% Load | 39.3mV | 8.4mV | 19.4mV | 12.9mV | Pass |
| 60% Load | 29.5mV | 17.1mV | 25.7mV | 20.2mV | Pass |
| 70% Load | 29.4mV | 9.4mV | 24.2mV | 14.7mV | Pass |
| 80% Load | 32.8mV | 10.4mV | 24.9mV | 16.4mV | Pass |
| 90% Load | 35.7mV | 14.0mV | 30.0mV | 21.2mV | Pass |
| 100% Load | 39.8mV | 25.0mV | 39.0mV | 33.0mV | Pass |
| 110% Load | 45.0mV | 27.5mV | 40.4mV | 48.5mV | Pass |
| Cross-Load 1 | 15.7mV | 10.1mV | 18.8mV | 5.1mV | Pass |
| Cross-Load 2 | 39.2mV | 27.4mV | 37.0mV | 34.6mV | Pass |
For a high-end CWT platform, these ripple suppression numbers don't live up to our expectations. The +12V rail might be close to 40mV at full load, which is quite good, but we're used to seeing less than 30mV (and in some cases less than 20mV) from platforms in this price range.
Worse, the 3.3V rail can't keep its ripple below 30mV. CWT should probably take a look at this rail's voltage regulation module.
Ripple Oscilloscope Screenshots
The following oscilloscope screenshots illustrate the AC ripple and noise registered on the main rails (+12V, 5V, 3.3V and 5VSB). The bigger the fluctuations on the screen, the bigger the ripple/noise. We set 0.01 V/Div (each vertical division/box equals 0.01V) as the standard for all measurements.
Ripple At Full Load
Ripple At 110-Percent Load
Ripple At Cross-Load 1
Ripple At Cross-Load 2
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