Differential Hall Sensor 437

Calibrating Wheel Speeds

In order to properly calibrate the wheel speed sensor in the ECU you must know the circumference of the tire. According to Geometry the circumfer­ence is equal to the diameter of the tire multiplied by Pi (3.14159). Unfortunately, your tire diameter will change when it is supporting the weight of the car. So the best way to get the tire circumference is to mark the tire and the ground, and then push the car until the mark on the tire is again back on the ground. Then measure the linear distance between the two marks. You can then divide this measurement into the distance you are calibrating for (1 mile = 5280 ft.). The result is the number of tire revs per mile or KM. Then we have to multiply this number by the number of teeth on the trigger wheel. Finally, the total is divided by 10 to arrive at the calibration value. Circumference = 8.3 feet 5280/8.3 = 636 Number of teeth = 4 so 636(4) = 2544/10 = 254.4 Calibration value is 254.4