FC CAS setup
 

Why does Haltech recommend when using the internal reluctor to have the trigger edge set to "rising" yet it is popular for us using the FC CAS to set the trigger edge to "falling"? Am I missing something or is the falling edge of the FC CAS more stable in it's relationship to the eccentric shaft.

It would seem that the rising edge of the signal would be more reliable than the falling edge since when the RPM increases the time between the two edges of the signal would begin to decrease. Or does this thought only apply to triggers that generate a square wave?

It simply has to do with the type of signal a particular sensor generates. Below I have attached a scope image of a typical VR sensor where the wave form crosses 0 from low to high. This would use a rising edge.

http://ludwigmotorsports.com/stock_cas_home.jpg


Now, image if you will that same trace running from right to left instead of left to right. The break across 0 is now going from high to low and would require a falling edge to work correctly. That is the signal that an FC CAS puts out and is why you need to run a falling edge.

Simply, a rising edge setting will not work with an FC CAS.

Thank you. That is beautiful information.