Operation

OPERATION

The ABM sends 12 volts to power an Integrated Circuit (IC) in the sensor. The IC supplies a constant 7 mA power supply to the ABM. The relationship of the tooth on the tone wheel to the permanent magnet in the sensor, signals the IC to enable a second 7 mA power supply. The output of the sensor, sent to the ABM, is a DC voltage signal with changing voltage and current levels. The ground for the IC and the current sense circuit is provided by the ABM.

When a valley of the tone wheel is aligned with the sensor, the voltage signal is approximately 0.8 volts and a constant 7 mA current is sent to the ABM. As the tone wheel rotates, the tooth shifts the magnetic field and the IC enables a second 7 mA current source. The ABM senses a voltage signal of approximately 1.6 volts and 14 mA. The ABM measures the amperage of the digital signal for each wheel. The resulting signal is interpreted by the ABM as the wheel speed.