I want to measure the power good time of ATX PSU using an oscilloscope.
As far as I know, normal time for power good is between 100ms to 500ms. and it is measured according to the picture below, starting from PS_ON command.
So I measured PS_ON and power good signals using oscilloscope and got the following image [I forgot to get the original piscture, so I drew it]
I think the power good should the time between PS_ON falling edge and PG rising edge. which is 180ms. But when i connected power supply to an ATX power supply tester (i borrowed cheap one with no brand name), it displays 280-320ms as PG.
Which measurement is correct. mine, or power supply tester?
Any advice to correct measurement is appreciated.
Thanks.