Let's test out this unit and see if it is what you are looking for:

For testing I will be putting the Coolmax USA LCD Power Supply Tester up against the internal voltage sensors on my  Gigabyte GA-X48-DQ6 using Speed Fan a popular free to use benchmark/monitoring software, which monitors voltages and temperatures. I will be testing two power supply's for quality control. The PSU's used will be the Mushkin 800W PSU I currently use and the Collmax USA 950 PSU I will be reviewing shortly. For the sake of simplicity I will only be listing the +3.3v, +5v, +12v, voltages.

Coolmax PSU:

The product designs with LCD to show ATX power voltage. Easy to plug with ATX power 24 pin and plug in (P4/P6/P8) to show the voltage on the LCD panel. Easy to check ATX power supply Aluminum case Accurate voltage indicator +/- 0.1V (+12V1/+5V/+3.3V/5VSB/+12V2/-12V) ATX P.G. value display Lower or higher P.G. values alarm ATX output connectors check Lower voltage detected alarm Over voltage alarm No voltage detected alarm Manual: Plug-in your ATX power 24 pin and plug-in (P4/P6/P8) into the tester. Turn on your ATX power supply LCD shows each voltage and P.G. value on the screen automatic and you can hear 2 beep sounds. ATX power output connector checking one by one. If power output is working, the LED will light on. If power output failed, the LED will not light on. Plug-in (HDD/Floppy) connector and check LED light (+12V1/+5V) Plug-in SATA connector and check LED light (+12V1/+5V+3.3V) Remove the connector after your checking Do not plug-in 2 connectors into the tester at the same time (Not include 24 pin connector) Abnormal voltage detected will not display on the screen. No voltage detect, “LL” will display on the screen. When detected Voltage is lower than Min. Value, “LL” will display on the screen. When detected Voltage is higher than Max. Value, “HH” will display on the screen. When detected voltage is lower than table value (A), will alarm. When detected voltage is higher than table value (B), will alarm. P.G. value detected lower 100ms or higher 900ms, P.G. value is abnormal and alarm. When abnormal happened, it will alarm and relative digit blink on the screen. Each Voltage normal range: +5V, +3.3V, +5VSB is ±5%; +12V1, +12V2, -12V is ±10% Each Voltage normal range: +5V, +3.3V, +5VSB is ±5%; +12V1, +12V2, -12V is ±10%   Normal Voltage range Display Voltage range     Lower (A) Higher (B) Min. (C) Max. (D) +5V 5.0V +4.75V +5.25V 4.0V 6.0V -12V -12V -11V -13V -10V -14V +12V1 12V 11V +13V 10V 14V +12V2 12V 11V +13V 10V 14V +3.3V 3.3V +3.14V +3.47V 2.0V 4.5V +5VSB 5V +4.75V +5.25V 4.0V 6.0V PG   0ms 990ms

We now see the draw back of using an internal sensor for your voltages. Speed fan is picking up the -3.3 volt as the +12v voltages. The internal sensors vary from motherboard to motherboard as well I have seen much stranger voltages from motherboards I have used in the past.

Mushkin PSU:

Again we see a weird variance between the 12v numbers. One thing worth noting is that the other voltages are very similar. I have also tested the Mushkin in the past with my multi-meter and the voltages are bang on with only hundredths of a volt differentiation between the two.

I tested two more power supply’s I had kicking around for de-soldering caps from, that I know where bad. Once I plugged them in and booted up the Coolmax USA LCD Power Supply Tester it beeped and displayed errors just like I hoped it would. The tester did very well in these tests, let's check out the final thoughts:

Overall the Coolmax USA LCD Power Supply Tester did incredibly well during testing. The voltages were bang on, the error message was clear as day, and the over all use was very straight forward. If you have ever had to use a multi-meter to test a power supply in the past you will be in Sto-vo-kor (uber geek heaven) using this multi-meter. The ability to turn on the power supply and test it all in one unit was impressive and takes a matter of seconds compared to the old testing standard.

As always the most important question is would I recommend it? Yes, and here is why, it was by far the easiest, most accurate, and fully functional tester I have used to date. The simple to read LCD beats the old LED color coded testers hands down. I recommend this tester for anyone, not just enthusiasts or major gamers. With this simple device which costs under $20 you can save yourself a pricey trip to your computer tech and find out if your power supply is the root of all of your problems instead of spending money for hours of tech work before he finds the issue.

Pros:

• Simple to use
• No Need to Power up your PC
• Easy to Read LCD
• Remarkably Accurate Voltages 

• The First few Times you Plug the 24 Pin Connector in it is a Bit Stiff (not really a con but something to keep in mind)