You could probably take it off the common rail diesel injectors if you needed to. An opto-isolator would protect it nicely from any back-emf.
I'd be interested to see how it works with the alternator - would you be trying to measure the fluctuations in voltage coming out of it?
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
You could probably take it off the common rail diesel injectors if you needed to. An opto-isolator would protect it nicely from any back-emf.
I'd be interested to see how it works with the alternator - would you be trying to measure the fluctuations in voltage coming out of it?