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TweakTown's New PSU Testing Methodology Explained

By: David Walker | Other PSUs in Cases, Cooling & PSU | Posted: Feb 14, 2009 5:00 am

Standard Tests


We measure each of the rails under load for voltage stability during all tests. If any voltages fall outside of the current ATX specification, they are denoted in red for easy identification. Stable voltage on all power rails within design limits is essential for a stable, reliable system. All measurements are measured at both ambient room temperature and at 45C operating temperatures in the hotbox.


In addition to the voltage reliability, we will also be measuring voltage ripple on the all important 12V rail with an oscilloscope with the proper capacitors in place to filter noise. Simply put, this measures how clean the power delivery really is for the tested power supply. Again, anything falling outside of ATX specifications will be denoted in red. Currently, the requirement is 120 mV for 12V.


Lastly, we will measure the efficiency of the power supply. There are a number of factors like power factor correction that can skew the results, but we will simply concentrate on the ratio of AC power drawn at the wall socket to the amount of DC power actually supplied within the system. Most modern power supplies will be over 80% efficient. Again, any results under 80% will be denoted in red. Please keep in mind these efficiency results are at 120V and will be slightly higher in countries with 220V power.



TweakTown's New PSU Testing Methodology Explained


Power Supply Features


Not only will you have all of the bench results, you will need some additional information regarding the power supply such as features, cable types, connectors and lengths. Again, in order to provide information in an easy digestible format, we have simply identified the common features that we look for in a power supply and note whether the power supply included the feature or not. Most of the time, we want to know what the power supply is missing versus combing through a generic list of features included. Exception management is much simpler, faster and easily compared.



TweakTown's New PSU Testing Methodology Explained



TweakTown's New PSU Testing Methodology Explained


Once we have a gander at the features included with the PSU, we take a quick count of the cable types, the number of connectors and measure the lengths to the first connector. If there is more than one connector, as in the case of a molex or SATA run, each subsequent connector is measured along the cable run.



TweakTown's New PSU Testing Methodology Explained


For example, looking at the Molex + Floppy results, we see there is one cable with two molex and one floppy connector. The first molex is 16 inches along the cable, the second at 22 inches, the third at 28 inches and the last floppy connector at 34 inches.


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