I got my first inline USB power monitoring gadget from Maplin in 2014. The review is here.
Now in 2015 I am pleased to report that the technology has become commonplace and the price dipped to practically nothing.
My source for these devices, and well as much as I can here in fortress Switzerland is of course eBay and I have a preference for Hong Kong and China sellers in that order.
I'm proud to relate that our IBM PC XT286 is still useful today. It forms the base of our charging station area :-)
An example gen2 product showing multiple metrics concurrently. Obviously I'm most interested in instantaneous Voltage and Current.
I speculatively ordered another unit or two, this one is my favourite since the display quality is astonishing.
I'll show the manual here though I don't use these facilities. Just Voltage and Amps for me please.
This unit has a welcome screen. I wonder if it is running an Operating System :-)
The quality of the display again
Currently then the best unit is from ebay seller kakasell8 in China 06.35 GBP including postage.
What a bargain.