- Sun May 29, 2022 7:34 pm
#57216
With standard sensor polarity (voltage falling on the trailing edge of the tooth), an inverted signal would actually be reading the rising voltage (falling inverted = rising) on the tooth leading edge. Worse, it will read the rising voltage in the middle of a missing tooth, as shown by the tooth logs below, confusing the processor.
The first image is correct sensor polarity, inverting conditioner, detecting Rising Edge.
The second and third images are reversed polarity Rising, and correct polarity but Falling edge.
Tooth logs are valuable to see what the processor "sees". One clean tooth gap works. Note: The first image may be incorrectly found with reversed polarity sensor, inverted, and Falling setting; but that configuration is prone to timing drift due to a factor called hysteresis.
Note 2: While Hall sensors are often claimed to be immune, this effect can also occur with those sensors. You can see the same effect in your first-post 'scope image, the conditioner square-wave signal with the odd "wide" tooth at the gap.
The height of each bar represents the time from one tooth to the next. A missing tooth (gap) then shows as a long time bar to the next. Two long time bars is reading the wrong edge, including one that doesn't exist in the gap. The first image, with correct sensor polarity, is the goal:
dener0987 wrote: ↑Sun May 29, 2022 1:50 pmAs for the Trigger edge configuration for inverter conditioners (Max, Lm1815) shouldn't the edge be Falling?No, as the output signal is being inverted, the signal is falling but the output is rising. Set for Rising Edge to read the falling sensor signal at the trailing edge of the tooth.
With standard sensor polarity (voltage falling on the trailing edge of the tooth), an inverted signal would actually be reading the rising voltage (falling inverted = rising) on the tooth leading edge. Worse, it will read the rising voltage in the middle of a missing tooth, as shown by the tooth logs below, confusing the processor.
The first image is correct sensor polarity, inverting conditioner, detecting Rising Edge.




The height of each bar represents the time from one tooth to the next. A missing tooth (gap) then shows as a long time bar to the next. Two long time bars is reading the wrong edge, including one that doesn't exist in the gap. The first image, with correct sensor polarity, is the goal:
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