I started doing a MUCH briefer answer to this question "What exactly is a Data logger - does it just measure lap times?" posed by capt Slow in this thread
http://openpitlane.co.uk/forum/showt...p?t=747&page=5
Finger trouble ended up with me throwing it away so decided, whilst in a few brief sober moments whilst on holiday, I would do an even fuller answer to the question as I do get asked this question a lot, and what to do with them when you've got one (upcoming post on that also). I typed this bit by bit in notepad and having found a free wi-fi hotspot decided to post it now rather than on my return.
Formatting is probably cr@p so, if it's too bad anyone with access is welcome to format it better.
Probably won't be able to answer questions/comments until Wed when I get back home.
Maxx