Reading signal from 190v magnetic pickup
"I am also using a precision 18bit ADC, so would a simple voltage divider to reduce the voltage to &lt;5v work? As a slow moving interrupter will produce a very low voltage anyway."

Yes in principle you can just use a voltage divider, however you have to be careful to take the power into account so that you don't burn your resistors. It is also important to note that the voltage you are measuring (+-190V) is most likely the unloaded voltage out of the coil, as soon as you put a load on it (ie. the voltage divider) then the voltage will drop.

If you go ahead with the voltage divider solution it would be a good idea to put a small capacitor (maybe 100p) across the output of the voltage divider to the MCU, and also to put a TVS diode or similar across the MCU input to protect it.

Other solutions exist but they involve turning the pulse into a logic level high/low pulse ie. you will loose the voltage information but I don't know if you need it?