mbaldini

thanks Paul. a running average would probably suffice. It is meant more for gauges and data logging so it will be much more forgiving than if I were using it to actually do things such a adjusting the spark timing. I will give it a try with a running average (perhaps based over a course of 100-250 ms) and see what sort of signals I get. And I will be mounting this inside the car under the dash, and I will ensure the power cables for the rest of the accessories are routed away from the netduino and its signal wires.

thanks! the electrical system in the car is about as simple as it gets. negative terminal grounded to the chassis, positive runs to a distribution block with a secondary wire to the starter. About the most complex part is the dimmer switch for the dash lights lol. 

anyway, the sensors do have their own ground wire. But I was wondering about noise.I know (with audio systems at least) the alternators can cause undesirable signal noise. I had used ground loop isolators for my stereo systems before, but didn't know if they would work here so I was looking to use some shielded twisted pair cable for the sensor leads.

So voltage dividers would in fact work for this setup? That Will simplify things quite a bit.

Now with the frequency based signals, I couldn't use a digital pin for these? they are a digital signal, so I was anticipating using them as a as an InterruptPort and simply keep track of the duration elapsed between interrupts to calculate the frequency. Would that not work?

forgot to mention some signals are 0-5 v and others are 0-10 v. it is the voltage difference between the sensors and the 3.3v that the netduino is expecting that I am asking about.