Dear Nick Gamon and El_supremo.
I realy appreciate your enlightment.
Hmmm ... second thought ....
What About this :
- Use PinChange For that 4 Flow meter (Low pulse per minute), and
- Use Frequency-to-voltage IC and feed the output to Analog pin to read the current engine RPM
Something that noted at http://www.jaycar.com.au/images_uploaded/LM2907.PDF page 7 (Minimum Component Tachometer) , Plus a voltage devider .
About periodic Serial.println .... could be done.
Maybe once per second ?
Sincerely
-bino-