ABS wheel speed sensors

I did the folowing tests on a daihatsu.The wheel sensor on this vehicle was a analogue type.I found that this was a analogueb type sensor because it had 2 wires goin to it and a digital type usaly has 3 wires sometimes more.I used the back wheel sensor because I coul not get to the front ones plug so was not able to see the amount of wires going to it.I was asked to measure the air gap for each wheel sensor.I could not do this because ther was a plate in the way and I did not have any tools to remove this.

This is an example of the type sensor the  vehicle I used had.
http://www.google.co.nz/imgres

I used a oscilloscope to get the patern for the wheel sensor.

This is A analogue pattern as I talked about before.
had it at 0.5v and 20ms