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Test Method: High-Precision Measurement Instruments

Soon At Tom's Hardware: Full-Scale Power Supply Testing
By , Patrick Afschar

The reliability of PSU testing depends on the test setup and the measurement instruments used. Since the significant differences can be small, you need high-precision equipment for them to be documented in a way that's both clear and reproducible.

The cornerstone of all of these measurements is a defined and stable input voltage. Using power straight from the wall socket is out of the question, since this power source is subject to several confounding factors that might lead to significant fluctuations. Instead, we use the high-precision Chroma AC Source 6530, ensuring that all tests are provided with accurate AC voltages of 115V and 230V at a perfect sine curve of 50 or 60 Hz.

We use the precision power meter Yokogawa WT210 for measuring the voltage and current fed by the Chroma. The device attaches directly to the power source and measures voltage, current, power, power factor, and frequency with an accuracy of about 99.9 percent. With a maximum input limit of 26A, it's ideally suited for monitoring the power consumption of high-performance systems.

Clearly-defined DC loads have to be simulated on the different individual rails during all of the measurements. Since this also requires precision instruments, we use a total of eight Chroma DC electronic loads from the 6330-series.

Four of these are capable of generating a maximum load of 600W each to be used as loads for the 12V rails. The remaining four Chroma DC loads (300W maximum each) are responsible for load generation on the 3.3V, 5V, 5V sb, and -12V rails. Three dedicated control units are used for the basic configuration and to recall programmed scenarios. All units come with a feature for generating a controlled short circuit.

We also use a modern oscilloscope, the Tektronix Scope DPO3034, for graphic processing of the measurement results. The four-channel, 300 MHz oscilloscope provides us with readings of voltage, current, frequency, ripple, and rise/fall time. Thanks to its integrated Plug'n'Play PC interface, LAN, and USB connections for external storage, the DPO3034 can be comfortably integrated with the rest of our IT infrastructure.

With the press of a button, a screenshot gets saved as an image file directly to the external storage device connected to the oscilloscope. Not least of all, our Tektronix TCP150 measurement probe is able to handle currents of up to 150A and is an important addition to the oscilloscope for monitoring current flow.

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  • 33 Hide
    Gamer-girl , June 22, 2010 6:24 AM
    Is it possible to include sound levels in decibels?
  • 27 Hide
    JonnyDough , June 22, 2010 6:34 AM
    I second what gamer-girl said, and although this is exciting I'm still awaiting the Graphics Comparison Charts! I realize this is more of an IT website, but these days everyone's a gamer of some type! Long live PC gaming!
  • 17 Hide
    baracubra , June 22, 2010 6:37 AM
    Wow, great idea and article! This will be a huge help and I'm glad u guys took the time and effort to put this together! Long live TH!
Other Comments
  • 33 Hide
    Gamer-girl , June 22, 2010 6:24 AM
    Is it possible to include sound levels in decibels?
  • 27 Hide
    JonnyDough , June 22, 2010 6:34 AM
    I second what gamer-girl said, and although this is exciting I'm still awaiting the Graphics Comparison Charts! I realize this is more of an IT website, but these days everyone's a gamer of some type! Long live PC gaming!
  • 17 Hide
    baracubra , June 22, 2010 6:37 AM
    Wow, great idea and article! This will be a huge help and I'm glad u guys took the time and effort to put this together! Long live TH!
  • 13 Hide
    Anonymous , June 22, 2010 6:42 AM
    take the good ideas from some other nice psu reviewers

    http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=153
  • 3 Hide
    joytech22 , June 22, 2010 6:50 AM
    I hope they do a large comparison, i want to see how my Antec TPQ 1Kw stacks up to some of the other manufactures.
  • 3 Hide
    baracubra , June 22, 2010 6:53 AM
    Btw, how much did all this eqipment cost TH??
  • 3 Hide
    Anonymous , June 22, 2010 7:15 AM
    This is great news. On a related note do you guys not do LCD monitor testing anymore?
  • 4 Hide
    gege , June 22, 2010 7:42 AM
    take the good ideas from some other nice psu reviewers [2]

    www.hardwaresecrets.com/page/power
  • 2 Hide
    liquidsnake718 , June 22, 2010 7:46 AM
    Bravo, good choice for a new section as more consumers and buyers should be aware of the power supplies and the quality/preformance that they offer us. I myself am about to change my older PSU and will be waiting to read the first comparisons. The problem is, which ones will you choose and every month will you have a power category? For example all the 500-600watts, then following the 700-800, 1000w onwards, ect.

    You might even succeed in killing off generic psu's or at least make more ppl buy 80 plus or 80plus bronze psu's....
  • 2 Hide
    Henry Chinaski , June 22, 2010 8:42 AM
    It's a very good news. Another qualified reviewer is always welcome.
  • 4 Hide
    KingArcher , June 22, 2010 9:09 AM
    This is an awesome setup. Wish I worked at TH.
  • -2 Hide
    neiroatopelcc , June 22, 2010 9:31 AM
    Article500W: Gaming PC with a high-end CPU and multiple graphics cards

    I've measured my system using 750W, and that's definetly more than 500W draw on the inside. And considering my system's only got two harddrives and air cooling, I'd say 500W doesn't qualify as high end cpu with multiple graphics! 600W at least!
  • -6 Hide
    Reynod , June 22, 2010 9:52 AM
    Great news.

    We should of course give the reviewer the nickname "Scotty" ... surely?

    The PSU is technically "engineering" and ratings should include references to "warp factor" and dilithium crystals" ...lol.

    Nice test gear there ... good looming job too.

    Looking forward to some definitive reviews now you have the gear.

    I am wondering how some of the vanilla PSU's will go against the more expensive units?

  • 1 Hide
    gustavost , June 22, 2010 10:13 AM
    I can't barely wait for the test!

    It's really nice that we as customers have real test we can rely on!
  • 0 Hide
    feeddagoat , June 22, 2010 11:08 AM
    Bit-tech/CPC already do something like this. Its by far the best way to test PSU's and its fantastic that Tom's is doing something similar. Can I suggest a comment on fan noise as well. bit-tech comment on the loudness of the fan at full load but don't actually do any sound measurments due to background noise in the offices. Better than nothing tho. Also is there anyway to "endurance test" a PSU. A few PSU's end up in secondary PC's, it would be nice if there was someway of testing long term strain on PSU's too.
  • -4 Hide
    7amood , June 22, 2010 11:19 AM
    YESSSSS PLEEEEEEEEEEEEEEASE \^_^/
  • 8 Hide
    allantang , June 22, 2010 11:56 AM
    I wish there were more info on this stuff, so this would be great!

    I think room temp should also be taken into account. It will make a huge difference if the room is 15C or 25C.
  • 0 Hide
    JohnnyLucky , June 22, 2010 12:13 PM
    Great news! Looking forward to reading power supply reviews. Glad to know you will be testing overload and short circuit protection.
  • 4 Hide
    saifallofjmr , June 22, 2010 12:19 PM
    Also please do the green series by rosewill so we can finally confirm whether or not this brand is in fact good or really bad.
  • 0 Hide
    elel , June 22, 2010 12:37 PM
    Good job. Another thing that I think would be VERY useful would be to test the current drawn from each rail by the SBM PCs. I know that you test system wattage already but I would like to see how much current of each voltage they draw, possibly taken from a custom modded high wattage PSU like the one x-bit made for similar measurements.
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