This is the most widely used type of ignition sensor. The Hall effect (named after the American physicist Edwin Herbert Hall, 1855-1938)
How Does It Work
A current is passed though a silicon wafer. When a exposed to a magnetic field this disrupts the current flow and distributes more "potential" on one side of the wafer. This can be measured, conditioned, and amplified to trigger the ignition module.
Hall Effect sensors are extremely accurate, they produce a "square" wave signal perfect for solid-state applications, and are very durable against heat / vibration. The rotor magnet does not need to be as strong (you may not feel its pull with a heavy screwdriver)
Most Hall effect rotors involve a stationary Hall Switch and stationary magnet. What rotates is an "Interrupter Blade". When the blade passes between the sensor and the magnet it blocks the magnetic pull on the Hall Switch. When a "shutter blade" is open, the magnetic field projects onto the Hall Sensor switching it on.
There are variations of the theme and type of trigger unit but this basic information only serves to give a brief run down of how they work, and should not be a consideration when trouble shooting a problem
The easy way to identify a Hall system is the fact that it must be externally powered. So, there's going to be that extra 12v wire feed usually on the red wire into the ignitor unit in the distributor.
How do I do a Basic Test on the hall trigger unit?
Place a low wattage bulb <2w. into a bulb holder, place the wire from bulb holder centre pin on the 12v connection and the other bulb holder connection onto the negative terminal of the coil. crank the car over with the plug leads off and you should see the bulb flash on/off.
Edited by KernowCooper, 28 March 2013 - 01:02 AM.