Guide to Selecting a PC Power Supply Using a Multimeter
Nowadays, new-generation components such as graphics cards, sound cards, optical drives, and hard drives are all power-hungry. When loading up your PC with all these parts, have you ever thought about equipping it with a strong, reliable heart - the power supply?
Many experts have already shared their methods for judging a power supply in various magazines and articles. In summary, there are three common approaches:
First - Visual InspectionCheck whether the internal components are of good quality, whether the workmanship is precise, and whether the layout is reasonable. To be honest, this method is somewhat demanding. First, it requires solid electronic knowledge. Second, to see the internal structure clearly, you have to open the power supply case, which will break the manufacturer's warranty seal. Once the seal is damaged, the warranty is void, and you have to repair any problems yourself. Many beginners are forced to learn the hard way this way.
Second - Touch CheckAfter the system has been running for a while, feel whether the air from the power supply fan is excessively hot and whether the case is burning to the touch.
Third - Smell CheckSmell for any burning or scorched odors after prolonged operation.
The latter two are purely based on accumulated experience, which most beginners simply do not have. So here I recommend a method to test a power supply using a multimeter, which may help new users.
First, prepare a multimeter (preferably digital) and know how to use it.ATX power supplies mainly provide outputs of 3.3V, 5.0V, and 12.0V. Among them, the 12.0V rail is the main power source for hardware devices and shows the most obvious changes under heavy load.With all computer loads connected, choose any unused connector. Insert the black probe into a black wire terminal (ground), and the red probe into a yellow wire terminal to measure the 12V output.
Turn on the computer and begin testing. You will see the multimeter reading fluctuate until the system fully boots and stabilizes. Record this voltage. Under normal conditions, it should stay around 12V - typically between 11.95V and 12.15V.A voltage that is too low cannot support stable operation under heavy load and offers no upgrade potential. One that is too high causes components to overheat and age prematurely.
Next, press the RESET button to restart the system. Watch the multimeter closely. During the power-on self-test, the voltage will reach its lowest point. Record this value.If the difference between the highest and lowest voltages is small (within 0.3V), the power supply is acceptable. If the difference is large, the power supply has poor load capacity and should be avoided.I once tested a 300W power supply that showed 12.32V at its highest but dropped to only 11.73V at its lowest, causing frequent system crashes.
Finally, observe performance under actual use. Run various software applications, play music through the optical drive, and stress all components. If the voltage remains stable without significant fluctuations, the power supply is a good choice.
