OK, well, I would say it's that calculated amplitude that matters then. The module sets a base level high current and saves it. Once corrosion or a pinched wire enters the playground, those peaks are unexpectedly low, and a fault is set. We are saying the same thing.

Some of the how is definitely reserved for the EE types... I was surprised they measured current and not voltage. That's where my knowledge was at.

There's also the possibility that older ABS modules did this differently. I was just trying to explain it. Maybe I made it more confusing.

 

AC by it's nature is digital; 0 or 1. The rise and fall part of the wave is basically ignored. Digital circuits actually see 5V or less than 5V. The 5V ref and low ref where low ref is usually digital ground but could be 4.9V if that was easier.