USB phone chargers - are all chargers equal

what is the standard for USB


can u compare the measure of amps and volts comming from my PC  vs a wall charger ? and are all wall chargers made equal?  

.I have been told some are 2 amp   others are one amp.... can anyone comment on this and  help me learn  ?
intelogentAsked:
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EirmanChief Operations ManagerCommented:
They all provide the same voltage (5 volts). Current allowed varies from machine to machine.
If you draw current above specifications, the voltage will start to drop (or a fuse may blow).

Minimum specifications From Wikipedia (many manufacturers allow more current to be drawn)..
The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices.
A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0.


You can buy special USB meters
http://www.amazon.com/AboveTEK%C2%AE-USB-Power-Meter-Current/dp/B00JIFMXSK/ref=sr_1_4?ie=UTF8&qid=1430665211&sr=8-4&keywords=usb+meter
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EirmanChief Operations ManagerCommented:
There is a widely recognised European standard which is gaining wider acceptance
http://en.wikipedia.org/wiki/Common_external_power_supply

A decent charger such as this has a CE quality mark and can deliver up to 2 Amps
without the voltage dropping below 5V.
I wouldn't bother with lower ratings.

Also look for ....
Surge protection
Temperature and short circuit protection
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intelogentAuthor Commented:
ok,

thanks...  do all usb ports of a computer output the same volts and amp.... and would you know what that is please   ?
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intelogentAuthor Commented:
i just ordered the meter... thanks
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