So I guess, back to struggling with timing... The issue is the calculations I make don't come close to the Trinity Motolyser. While the calculations do increase and decrease when changing the timing on a motor and compare across motors, the values are off and not by the same coefficient. I am attaching screen shots of 3 different motors. The first is an v21s (21.5), the second a slot machine (21.5) and the third an mc4 (17.5).

Trinity Motolyser readings are as follows:
v21s - 42.1*
SM - 45.2*
mc4 - 38.9*

My calculated values:
v21s - 56.5*
SM - 58.2*
mc4 - 56.1*

The measurements are done vs sensor c and phase c
My calculation is (1/frequency of motor)/360 to get degrees per second. Then take the time difference between the rising edge of the hall sensor - the guestimated zero cross of the bemf on phase c. The zero cross will be about halfway through the first small rise. The output is only showing half the bemf wave. The cursors in the pic show where I am calculating from and the delta is calculated by the scope.

Anyway, delta time/ degrees per second = degrees timing.

What am I missing here? I can use comparators to get a real zero cross, but I doubt it will account for 15-20* difference. And if that number just stayed the same, it would be easy.

R1 v21s 21.5



Trinity Slot Machine 21.5


Motiv MC4 17.5