? on Mr Hall Effect

[Mike Turner]

Most current generation hall effect sensors have a magnet in the assembly.
The metal tooth being sensed alters the flux that the sensor sees from the
embedded magnet. The sensing element itself detects a level of magnetic
flux. Either you may have and sensor without the embedded magnet and need a
magnetic source or you need something ferrous to sense with the existing
magnet and sensor. The output should be static ie. if the tooth is present
the output should be low and if the tooth is absent the output should be
high. Too large a gap between the sensor and sensed object will also cause
no change in output. Some sensors also use an open collector or open drain
output and need a pull-up resistor on the output. I am using several Hall
sensors to sense wheel rotation and have not seen the problem. Do you have
a manufacturer and a part number? I think I can help here.