How does a ABS magnetic ring work?

To understand how an ABS magnetic ring works, we can imagine it as a "magnetic speedometer." Unlike older systems that relied on gears, it uses magnetism to transmit information.

▪ The "Arrangement" of Magnetic Poles

Invisible Scale: The surface of the ABS magnetic ring may look like a smooth rubber or metal ring, but internally, it's like a magnet, with many tiny positive (N) and negative (S) poles arranged uniformly.
Magnetic Code: These positive and negative poles are like a string of binary code, with dozens of pairs in a single rotation. They rotate rapidly with the wheel.

▪ The Sensor's "Scanner"

Close Observation: An ABS sensor is positioned directly above or to the side of the ABS magnetic ring.
Capturing Changes: As the wheel rotates, the positive and negative poles on the magnetic ring alternately pass by the sensor. Each time a magnetic pole passes, the sensor detects a change in the magnetic field.
Translating the Signal: The sensor converts this magnetic field "pulsing" into an electrical signal and sends it to the car's computer. The faster the wheel rotates, the more frequent the electrical signal pulses.

▪ The Computer's "Logical Judgment"

Comprehensive Comparison: The car's computer simultaneously monitors the signals from the ABS magnetic rings of all four wheels.
Detecting Anomalies: If, during braking, the computer detects that the signal frequency from one wheel suddenly slows down or even disappears (meaning the wheel is about to stop rotating, or "lock up"), while the other wheels are still sending signals rapidly...
Quick Reaction: The computer will immediately order the braking system to "release" that wheel! This is why you feel the brake pedal "pulsing" during hard braking.

▪ Why Does It Malfunction?

Vacuum Cleaner Effect: Because it's magnetic, it easily attracts fine iron filings or metal powder from the road surface. If this debris covers the ABS magnetic ring, the sensor can't "see" the signal clearly.
Installation Direction: If it's installed incorrectly during bearing replacement (the magnetic side isn't facing the sensor), the system will immediately report an error, and the ABS light on the dashboard will illuminate.