engine rpm signal

Projects General Guidance
1

Can arduino read reliably rpm of the internal combustion engine via negative injector signal? I am looking at the 0-17k rpm. Can I use 2n3906 transistor to read it reliably or should I get a Schmitt trigger?

2nd question, can I read exact time in milliseconds the amount of the time that the injector stays open, once again, needs to be pretty reliable.

Thanks.

2

You should be able to do this, but you will need to design some interface circuitry which can present a clean signal to an Arduino digital input. Unless you know exactly what the signal looks like you will have to experiment with it.