|CoolMax CUQ-1200B Modular 1200W Power Supply Unit|
|Reviews - Featured Reviews: Power|
|Written by Olin Coles|
|Sunday, 25 November 2007|
Page 4 of 5
I am well aware of what the more knowledgeable readers think about these power supply reviews: impractical and often useless. Benchmark Reviews is working hard to change that impression. Recording voltage with a digital multimeter alone offers no value to the test, since power fluctuates a great deal in the span of a single millisecond. Because of this, Benchmark Reviews has taken a corrected approach to testing PSU's and hopes to offer the best analysis possible.
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, energy efficiency, voltage regulation, and current ripple. Each of these variables must be analyzed with unique tools, which makes it properly review a power supply unit without them.
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 power supply units worth $100-$300. 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. Additionally, the CyberPower CP1500AVRLCD 1500VA 900W LCD UPS reports the total power load drawn by the system. Used together, the Oscilloscope. LCD UPS, and digital multimeter will offer readers the best measurement of power stability any review site could reasonably offer.
Test System (200W Idle / 280W Loaded)
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. Over time, there have been many changes to the test environment in terms of system hardware and software versions. We understand that consistent in our testing methods is very important in order for the results obtained to be comparable.
At the start of every test, the Velleman PCSU-1000 Oscilloscope is calibrated with 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. These readings are displayed several times per second, so a visual inspection of the most common (average) reading is recorded for our test results.
After the results have been recorded from the light idle load, our test system then receives heavy load by utilizing ATITool to scan for artifacts. This forces the video card into high-power 3D mode, and after many months of research this program alone has proven to create more power draw than the Folding at Home clients or a combined EVEREST System Stability Test. After another minute 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 might 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 Waveform at Light Idle Load
The waveform image above shows the AC power ripple under light idle load, which is measured inside of a 1ms recording frame. Waveform data recorded during the light idle load measurement is represented in the chart below:
AC Ripple Waveform Data at Light Idle Load
The waveform data above describes the actual measurements at light idle load. The maximum peak-to-peak AC voltage distortion was 190.6 mV, and the AC RMS ripple was 24.2 mV under light idle load. Note that these results are slightly better than the average results we have collected under light idle load.
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. The maximum peak-to-peak AC voltage distortion was 232.8 mV, and the AC RMS ripple was 30.85 mV under heavy load. Note that these results are only slightly better than other test results we have collected under heavy load.
AC Ripple Waveform at Heavy Load
Under heavy load, the CoolMax CUQ-1200B Modular 1200W Power Supply Unit measured an average AC RMS ripple just a little higher than the ripple at light idle load, which is very good. The waveform data recorded during the heavy load measurement is represented in the chart below:
AC Ripple Waveform Data at Heavy Load
Because the CoolMax CUQ-1200B 1200W PSU offered above-average results in the idle readings, I didn't really expect them to get any better; but this PSU recorded excellent results into the heavy load tests. 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 12.00 V, which means that even under heavy load there is almost no chance that system stability will be affected. Under light idle load conditions the DC regulation averaged 0.19 Vpp, and deviated only slightly more under heavy load to a measured 0.25 Vpp; both results are excellent. 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.