So a few months ago, I stumbled upon a thing at Adafruit.com called a "Charger Doctor" which was really just a Multimeter designed to slip inline with your USB cable. It was $7.50 and I liked it.

To measure a zener diode’s breakdown voltage, you need a dc voltage source whose voltage exceeds that of the zener voltage. In Figure 1, resistor R SER provides voltage drop between V IN and V ZEN. In ...

Fluke Corp. has introduced a new, easy-to-use utility multimeter designed to help utility workers, linemen and electricians, to quickly diagnose electrical problems. The Fluke 113 Utility Multimeter ...