Multimeter +

Multimeter
A multimeter or a multitester, also known as a VOM (Volt-Ohm meter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter would include basic features such as the ability to measure voltage, current, and resistance. Analog multimeters use a microammeter whose pointer moves over a scale calibrated for all the different measurements that can be made. Digital multimeters (DMM, DVOM) display the measured value in numerals, and may also display a bar of a length proportional to the quantity being measured. Digital multimeters are now far more common than analog ones, but analog multimeters are still preferable in some cases, for example when monitoring a rapidly-varying value.
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Turnigy 870E Digital Multimeter w/Backlight $5.99 at HobbyKing

expired Turnigy 870E Digital Multimeter w/Backlight $5.99 at HobbyKing

HobbyKing have recently released a multimeter at a good price. It comes up as $5.54 when I am logged in, so be sure to log in to your account for a potential discount.