Ripple Measurements

In the following table you will find the ripple levels that we measured on the main rails of SPS-750C. According to ATX specification the limits are 120 mV (+12V) and 50 mV (5V & 3.3V).


Ripple suppression on the minor rails is excellent. Unfortunately we can't say the same for +12V where ripple reaches almost 90mV, a value that may be 30mV lower than the ATX limit but is not what we expect from a modern, good PSU.

Ripple at Full Load

In the following oscilloscope screenshots you can see the AC ripple and noise that the main rails registered (+12V, 5V, 3.3V). The bigger the fluctuations on the oscilloscope's screen the bigger the ripple/noise. We set 0.01 V/Div (each vertical division/box equals to 0.01V) as standard but sometimes we are forced to use 0.02 V/Div, meaning that the fluctuations will look smaller but actually this wont be the case. For the first screenshot we used 0.02 V/Div, so actually the registered ripple is much bigger than it seems (compared to the other screenshots where 0.01 V/Div was used)

Ripple at Crossload 2

For the first screenshot we used again 0.02 V/Div. As above the order of images is +12V, 5V and 3.3V.