thanks IRstuff & zappedagain.
looks you both think the variation should be very small at the same conditions..
my concern is how to define the "degree". how much small value will be acceptable? otherwise it shows the PSU is abnormal.
when we do environmental stress test for PSU products, we'll perform function check before and after test. The function check include regulation, ripple current measurements etc..
Generally, the parametric data will change between 2 function checks even though the data are all within spec...
