I am trying to make a tachometer for my car. I am using a MSD6Al-2. The box outputs a 12 volt square wave at a 20 % duty cycle
I talked to someone at MSD and they said you'll get a signal every time it sparks.
The problem is it can spark up to 10 times per cylinder up to 3000 rpm. Now when tried to figure out the RPM if I just don't account for the muti-spark the numbers are better.
I am having trouble trying to figure out what RPM it is turning at.
Here is what I was doing:
number of sparks in the purple area divided by the number of cylinders (6) then doing that mutiplied by how many times that would happen in one minute.
Here are the images of the waves I got from my scope:
If anyone know how to find the RPM from this please let me know.
Also, what does the negative wave mean and should I count those too?