The inexpensive USB voltmeter ammeter combination is a handy tool to have. Whether your tracking down a problem, or just charging some batteries. No workbench or field kit is complete without one.
I bought this one on Ebay for $2.79, and it was delivered to the USA in just six days. There are more expensive versions with LCD displays, integrated USB cables, and other features. This simple model fills all of my needs.
I have three main uses for the tester:
- Checking the output voltage of a USB power source.
- Measuring the amperage that a USB power source can provide.
- Getting information about the condition of batteries being recharged.
For example, a 3.7v, 1S battery for my Syma X5C-1 quadcopter is rated at 500mAh. One battery typically charges at a current of 0.5 amps (500mA). When nearly fully discharged, it will take approximately one hour to recharge. Since 500mA for one hour is the rated capacity, I have a pretty good idea that the battery is healthy and up to specification.