How to Test and Tag a USB Charger

Main points to remember:

  • The AC side of the USB charger must be tested (the side that plugs into the wall)
  • Visually inspect and check the pins for protective insulation
  • Faults can be detected during Class II Insulation resistance or Class II Leakage Tests

Test & Tag Training have discovered that there's quite a bit of confusion surrounding how to test and tag USB chargers, or if they should be tested at all. 

Although USB chargers produces low voltage DC electricity and the standard states that you dont need to electrically test anything under 50V, this is not the case in this scenario. USB chargers still need to be visually inspected and electrically tested on the AC side of the transformer (the side that plugs into the wall) as this side carries 240V AC Current.

Like with all tests, the visual inspection is the most important - make sure there is no damage to the charger casing or pins. A cracked or damaged case could come apart, thereby exposing the live mains power components inside. With only two pins on these chargers they are prone to being bent if not plugged in or being unplugged roughly. 

All phone chargers in the market are currently Class II items and not only should they have the Insulation Resistance test performed, but also the Leakage Current due to the presence of electronic components in the charger. The easiest way to conduct our test is to leave the USB cable plugged in, as the metal end that plugs into your phone gives you something easy to attach your clamp or touch your probe to. This is much easier than trying to contact the small edge of the USB socket without making contact with the live components inside the charger.

For test tags that perfectly fit along the USB charger, try our surface mount pass tags.