PortaPow USB Power Monitor / Multimeter / DC Ammeter for Solar Panels, Mains Chargers, etc
This multi-meter plugs directly into any USB socket and allows you to connect any USB cable into it for charging or data transfer. It displays on screen the voltage and current which is being output, acting as both a volt and amp meter.3 inch extension flexible cable means you can turn the LCD screen to face you - unlike 'all in one' designs it won't be fixed facing the floor/wall regardless of how the USB socket is oriented.Uses a switch to change the display between current and voltage. No need to wait 10 seconds for the display to change as with alternative products.The meter is useful for solar panels with USB outputs, since it will then allow you to position the panel to maximize the energy it outputs, see what factors affect the panel's performance, and also to see when the output is too low to be worth using the solar panel. It uses an LCD display which is still easily visible in daylight - rival LED models can not be easily seen in bright sunlight.It is also allows you to compare the power of different USB sockets and study the quirks of USB charging. It has an upper limit of 3A.Updated Jan 2014 - Now with improved build quality and components. Please ignore older reviews which refer to a previous model.