Sensor Identification - Hall Switch

Hello all,

Quick intro first - I am an engineer with significant programming experience and have been playing around a little with arduinos.

My current project is an ECU system for an 80cc quad bike - I am trying to use the existing crank sensor on the bike but I am not sure exactly what it is, how to power it (as it only has one wire), and what output to expect from it. The sensor itself is magnetic and is clearly triggered by a lump on the wheel - this leads me to think that it is a hall switch of some form.

Would you mind please helping me identify what it is and how to read an output from it? Have attached a photo of the sensor (circled in red) and the wheel with the lump (also circled in red) on it.

Kind regards,

An engineer would have measured the resistance to ground to see if it had continuity. I really suspect it is the magneto for the spark plug.


Hi Paul,

Cheers for the tip - will check resistance next. I'm fairly sure it's an input from a CDI unit so I doubt that is the case.

It seems to generate approx 100mV when you put metal to it / away from it - that would indicate that it's a variable reluctance sensor wouldn't it?

Not all engineers are as smart as you may think... :slight_smile:

Kind regards,

Given the conditions the sensor has to put up with and that with the normal velocity of a magnet passing the sensor I believe that a reluctance sensor is more suited to application.

See about the difference in sensor types.

Thanks Zardozbighead - I think it might be a VR sensor. Will chuck the wheel + sensor on a lathe and check the output on an oscilloscope to confirm.

So it is a VR sensor. Here is the output from an oscilloscope with a piece of metal whizzing past the sensor on a lathe:

oscilloscope output.png

oscilloscope output.png