Quote:
Originally posted by Norm
Thanks for the info. Any input as to why the field would weaken over time? Resistance change in the coil? Magnet on the cam gear loosing its flux?
Norm
|
Yes Norm, its the magnetic field that becomes weaker over time. Heat and vibration are the things, that cause the field to weaken. The magnet is in the pick-up, with the winding wound around it. the cam gear just has a tooth that bridges the magnetic gap as it passes by.
In some other engines that use this type of magnetic pick-up, the flux gap around the magnet core, becomes bridged by metal filings. this shorts some of the magnetic flux out, at the case, reducing the flux across the pick-up gap, and hence the signal.
The output of these sensors depends on the strengh of the field and the speed of rotation. This why they can give so much trouble when starting, when the speed is slow, and its ok when running, due to the speed.
Harvey.
