Power adapters are a bit like canned food. Some manufacturers put a lot of information on the label. Others put just a few details. And if there is no information on the label, proceed with extreme caution.
The most important details for you and your delicate electronics are the voltage and the current. Voltage is measured in volts (V) and current is measured in amps (A). (You’ve probably also heard about resistance (Ω), but this doesn’t usually show up on power adapters.)
dc power connectors - round
To understand what these three terms mean, it helps to think of electricity as water flowing through a pipe. In this analogy, the voltage would be the water pressure. Current, as the term implies, refers to the flow rate. And resistance relates to the size of the pipe. Tweaking any of these three variables increases or decreases the amount of electrical power sent to your device. It’s important because too little power means your device won’t charge or operate correctly. Too much power generates excess heat, which is the bane of sensitive electronics.
The other important term to know is polarity. For direct currents, there is a positive pole (+) and a negative pole (-). For an adapter to work, the positive plug must mate with a negative receptacle or vice versa. Direct current, by nature, is a one-way street, and things just won’t work if you try to go up the downspout.
If you multiply the voltage by the current, you get the wattage. But the number of watts alone won’t tell you if the adapter is right for your device.
If the manufacturer was smart enough (or compelled by law) to include the DC output on the label, you are in luck. Look at the “brick” part of the adapter for the word OUTPUT. Here, you’ll see the volts followed by the direct current symbol and then the current.
The DC symbol looks like this:
To check the polarity, look for a + or – sign next to the voltage. Or, look for a diagram showing the polarity. It will usually consist of three circles, with a plus or minus on either side and a solid circle or C in the middle. If the + sign is on the right, then the adapter has positive polarity:
To check the polarity, look for a + or – sign next to the voltage. Or, look for a diagram showing the polarity. It will usually consist of three circles, with a plus or minus on either side and a solid circle or C in the middle. If the + sign is on the right, then the adapter has positive polarity:
If there is a – sign on the right, then it has negative polarity:
Next, you want to look at your device for the DC input. You’ll usually see at least the voltage near the DC plug receptacle. But you also want to make sure the current matches, too.
You might find both the voltage and the current elsewhere on the device, on the bottom or inside a battery compartment cover or in the manual. Again, look for the polarity, by either noting a + or – symbol or the polarity diagram.
Remember: the input of the device should be the same as the output of the adapter. This includes polarity. If the device has a DC input of +12V / 5.4A, get an adapter that has a DC output of +12V / 5.4A. If you have a universal adapter, make sure it has the proper current rating and that you choose the correct voltage and polarity.
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