|Thermaltake Toughpower W0133RU 1200W Modular PSU|
|Reviews - Featured Reviews: Power|
|Written by Olin Coles|
|Tuesday, 03 July 2007|
Page 5 of 6
PSU Load Testing
Power supplies are not like most other computer components, where it is a simple matter of comparing the item to others in the same category. Power supply's are comprised of several different variables, such as maximum output, voltage regulation, and current ripple. Each of these variables must be analyzed with unique tools, which makes it a difficult product to properly review.
I am well aware of what the more knowledgeable readers think about these power supply reviews: impractical and often useless. That's about to change. In the past, Benchmark Reviews has been guilty of the same thing nearly all of the other sites are guilty of: testing with a digital multimeter alone. This is why we are taking a corrected approach to testing PSU's and hope to offer the best analysis possible.
Benchmark Reviews has researched the equipment necessary to complete the most thorough power supply unit review possible. We spent the time learning what it takes because the best possible PSU tests are what we want to give to our readers. But after discovering the prices on a programmable output DC power supply system, variable range load testing units, and a DC power analyzer (Oscilloscope), we felt that more than ten-thousand dollars worth of equipment would be far too cost prohibitive for testing a hundred-dollar power supply. So without compromising too much, we made a slightly less-expensive investment into a good quality Oscilloscope in order to test DC voltage regulation and AC power ripple. Together, the Oscilloscope and digital multimeter will offer readers the best measurement of power stability any review site could reasonably offer.
Our testing process is comprised of measuring the AC current ripple, and the DC voltage regulation. There are several key steps, all of which allow us to measure and record our readings using the identical methods for every test we perform. Consistent testing methods are key to obtaining comparable results.
At the start of every test, the Velleman PCSU-1000 Oscilloscope is calibrated to the PC-Lab2000SE software. After calibration is complete, the voltage on the 12V rails are measured and recorded with the Extech 450 digital multimeter to ensure comparable margin across all rails. Once the Velleman 60MHz probe has been grounded and attached to the 12V lead, our test system is powered on and left at the Windows logon screen for ten minutes.
Once this lightly-loaded idle warm up period is complete, the Velleman PCSU-1000 Oscilloscope was allowed to run for one minute measuring the AC power ripple. Then once ripple is recorded, the 12V DC voltage regulation is recorded after another minute.
After the results have been recorded from the light idle load, our test system then receives heavy load by utilizing the following tools: two console versions of the Folding @ Home client operate and task each CPU core to 100%, hard disks are stressed by benchmarking each with HD Tach RW, system memory (RAM) is given a stress test with Lavalys EVEREST, and ATITool scans for artifacts which forced the video card into high-power 3D mode. After ten minutes of heavy load the power supply is again measured, and the AC power ripple and 12V DC voltage regulation results are recorded.
Voltage Regulation & Ripple Test Results
In the test results below, it will be necessary to explain what you are viewing. In each image the AC power ripple is represented by the yellow trace line making up the waveform. While every personal computer power supply unit available to the retail market has some degree of measurable AC power ripple, it is most important that measurable AC ripple is very minor and does not create a large peak to peak voltage (Vpp) distortion. Stable, well-regulated power is critical to system stability and hardware longevity.
AC Ripple at Light Idle Load
The waveform image above shows the AC power ripple under light idle load, which measures 11.28 mV. Note that there are several minor ripples above and below the baseline, and no major ripples, all of which occur inside of a 1ms recording frame. The waveform data recorded during the light idle load measurement is displayed in the chart below:
AC Ripple Waveform Data at Light Idle Load
The waveform information above describes the actual measurements at light idle load. The maximum peak-to-peak AC ripple was a mere 129.7 mV, which is the best we have recorded to date.
Here are the average AC RMS ripple measurements under light idle load for power supplies we have recently tested:
The waveform image below shows the AC power ripple under heavy load, which measured 12.70 mV. Note that there are several minor ripples above and below the baseline, and only a few major ripples, all of which occur inside of a 1ms recording frame. Now let's see how this power supply performs under heavy load:
AC Ripple at Heavy Load
Under heavy load, the Toughpower W0133RU measured an average AC RMS ripple of 28.76 mV, which is moderately low. For more specific readings, see the waveform data table below.
AC Ripple Waveform Data at Heavy Load
The Toughpower 1200W recorded great results in the idle readings, and they were still very good under heavy load. Here are the average AC RMS ripple measurements under heavy load for other power supplies we have recently tested:
The power dropped down to no less than 11.88V, which means that even under heavy load there is very little chance that system stability will be affected. Under light idle load conditions the DC regulation averaged 0.38 Vpp, and the deviation increased to .50 Vpp under heavy load. The DC regulation data recorded at light and heavy load is displayed in the chart below:
DC Voltage Regulation Waveform Data at Light Idle and Heavy Load
Many of the power supplies we test here at Benchmark Reviews have DC voltage regulation measuring above the 12V baseline more often than below. For obvious reasons, the diversion from the 12V baseline with increased voltage is more preferred than below it since dropping too far under 12V will cause a system to power off or recycle. Plainly put, no power supply is ever perfectly centered at 12V DC; instead they most often maintain a DC mean voltage higher than they are regulated at.