User:Lynnae/How to Test an AC Adapter

Tools

• Digital Multimeter

Keywords

Volt Amp AC Adapter Transformer Wattage

An AC/DC adapter (commonly known as an AC adapter) is used to change alternating current (the kind of power that comes from a wall outlet) into the electrical signal used by most consumer electronics, direct current, or DC, generally at a lower voltage. Most consumer devices that plug directly into the wall without an adapter have an internal AC power supply built in, to achieve the same result. For a laptop, an AC adapter minimizes internal components needed, and allows for the laptop to accept power from different sources. For instance, if you were to take your Laptop abroad, you'll soon note that many countries use a higher voltage than the United States when delivering power from the wall. In the US, 120 Volts is standard output. Note the input tolerance ratings on the back of your laptop's AC adapter: Almost all will accept much higher voltages than US standard power, and still deliver the needed DC output.

Take this IBM AC adapter as an example:

INPUT: 100-240V~1.9A
       50/60Hz
OUTPUT: 16V 4.5A 

[As well as a symbol that describes the polarity of the power supply, which won't be covered here]. From this information, we can see that the AC adapter will tolerate the incoming 120 Volts just fine, and will output 16 Volts, and 4.5 Amps. Amperage is another measure of the power delivered to the laptop. Many laptop AC adapters also list the wattage of the supply: Wattage is voltage multiplied by amperage.

...HOW TO SELECT THE PROPER AC ADAPTER

There are a few primary components that make up an AC adapter. If you find an old, clunky AC adapter and open it up, you will see a metal square with two sides wrapped in wire. This is called a transformer. Depending on how the sides of the square are wound, a transformer is used to increase or decrease the incoming voltage, and send it on to the rest of the circuit. From there, the AC signal is converted to DC by a part called a rectifier, and additional circuitry components may be present to regulate and smooth out the signal. Modern adapters use much smaller transformers, and more complicated circuits, and thus are lighter, and do not generate as much heat.

To test an AC adapter, you will need a Digital Multimeter. Set it to .... TO BE CONTINUED