Because the testing methodolgy is constantly evolving, the following
pages have been extracted and re-compiled from several different
pages. Therefore, it may
seem a bit disjointed. Just as the testing methodology is a work
in progress, so are these pages. Please accept my apologies in
advance.
TESTING METHODOLOGY:
For testing power
supplies, a SunMoon automated power supply load tester and a
Weibo PF1211 are used. The Weibo reads the Volts,
Amps, Watts
and Power Factor on the AC input of the power supply.
My dining room is now a mess. With a power supply
tester, mains diagnostic machine, notepad, PC repair bible,
a bunch of opened up power supplies, Black and Decker cordless
screwdriver, laptop, calculator... I won't be eating
in here for some time.
The SunMoon load
tester can dynamically load a power supply at the push of a button.
The SM-268 model shown on this page has five memory settings
and the ability to manually crank up the amperage while
the power supply is already up, running and loaded.
I will actually
program the loads each time I am given a different power supply
to test. The loads are based on the overall capability of whatever
power supply I'm looking at.
In the lower left
of the SunMoon is the cluster of power connectors that I plug
the power supply into.
Here you can see this Raid Max under a 366.8W
load, but pulling 485.6W from the mains. That's an efficiency
of 75%. Notice the Comp-Nurse on top of the power supply.
You can see here that I've loaded up the 12V
to 20A, the 5V to 20A and the 3.3V to 3A. The -5 and
-12V are getting a half of an amp load and the 5VSB gets a
2A load. You can tell these three pictures were taken
in sequence if you look at the Comp-Nurse. Notice the
temps getting higher.
Under this load, notice how the 12V is at 11.31. Well
under the 5% Intel allows for ATX specifications. In
all fairness, this power supply is rated with a more capable
5V rail, since I'm loading the 12V up to 20A, it's voltage
drops. This makes it a good power supply for a Prescott
with an AGP card or an AMD64 with a PCI Express card, but not
a Prescott with PCI Express and certainly not SLI.
The
display on the SM-268 has six fields. Each one representing a
loaded rail. There's a display for the 12V rail, 5V, 12V2 if I'm testing
a
dual rail power supply or -5V if I'm testing a single rail power
supply, -12V, 3.3V and 5V stand by. With the press of a button, the
displays
will switch from load in amps, to voltage, to wattage. In wattage
mode, I also get a display telling me the total wattage being loaded
onto
the power supply.
Now
to calculate efficiency...
Let's
say we have a power supply plugged into the Sun Moon and it says
it's pushing 300W. Now I'll take a look at the PF1211
and see how much
wattage I'm getting from the mains. If it says 500W, I divide
500W by 300W and come up with 60%. This would mean the
power supply is running
at 60% efficiency. The PF1211 also tells me my power factor
as well.
Busting out the old school calculator and notepad for this test.
Along
the bottom of the display of the SM-268 is a number of buttons. It's
quite intimidating and sometimes to accomplish something you have to
push a "shift" button and another button simultaneously.
I have most of my settings pre-programmed, so all I have to do is select "memory
1," through to "memory 5." I then have an up and down
arrow for increasing and decreasing load while the tester is
running.
For the record (because
someone asked me this the other day) the preset loads that I
have pre-programmed into the SM-268's memory DO NOT ramp up.
The load on
the PSU is immediate, so not only does the Power Good signal
on the power supply have to work correctly, but the power supply
also has
to be able to accept a sudden, nearly crushing load, in a split
second's notice.
