Reluctor Polarity

[bc201081]

I am in the process of doing an EFI conversion using a Atom G4+, the trigger setup consists of a 36-1 trigger wheel & a Ford EF reluctor pickup. I thought I would check the polarity of the signal using an oscilloscope, I was expecting to see a waveform like in the Link help file with a increasing rise & sharp drop, the wave form i am seeing on the scope is a symmetrical sine wave, this has me a bit confused on how to determine the correct polarity. Can anyone offer any advice?

 

[Adamw]

Yeah that can happen when the tooth width Vs spacing is relatively symetrical.  You will often still see a slight wave on one edge while the other (correct) will be straighter but I have seen a few where I couldn't confidently tell.  

Two easy ways to verify:

1. Suck it and see...  Get the engine running, make some very crude adjustments to get it running OKish, lock the timing, then give it a rev, if it is wired correct polarity the timing will be stable - say less than 1deg drift.  If it is incorrect polarity you will see significant drift - say more like 10deg. 
2. Multimeter test - Connect a multimeter to just the sensor, set it to DC mV range, stick a spanner or similar iron object to the end of the sensor, quickly move the spanner away while watching the multimeter display, It will only briefly flash to either a small positive or negative voltage.  If it flashes to negative as the spanner is snapped away, then your multimeter positive lead is connected to the sensor positive pin.    

[bc201081]

Thanks Adam, I have the engine running OK so I'll try your first suggestion.