G68 - Vehicle Speed Sensor Info please

[Error404]

Can anyone tell me some info about the G68 vehicle speed sensor?

Specifically, what type of sensor it is, how it works and how many impulses per wheel rotation / per mile/km?

Thanks
Alex

[driftin jo]

As far as I know it's a VR, (variable reluctance) sensor and works on the output shaft
with a toothed wheel in the box, the same way a abs sensor works on the CV joint.

I don't know how many pulses/ teeth per rev it has but I suppose it could be measured.
Maybe someone with in depth knowledge of the ECU may know.

[Error404]

Thanks
So as it is located on the front diff on the 01E, likely the sensor picks up an impulse from a tooth or teeth on the front diff.
It would be useful if anyone knows the number of impulses per rotation, or how to measure that?

[Error404]

I just found this which Aaron (SpeedingG60) posted on MG:

[driftin jo]

So it's a reed switch ?
Does this mean the output has some magnets on it ?

[Error404]

I guess so, I'm yet to take the diff cover off a gearbox to find out. I am surprised that a reed switch is reliable enough, but they never seem to go wrong...

[UrS4boy]

G68 Speed Sensor Info

Can anyone tell me some info about the G68 vehicle speed sensor? Specifically, what type of sensor it is, how it works and how many impulses per wheel rotation / per mile/km? Thanks Alex

It generates impulses as the teeth on Item 8 pass the nose of the G68 sensor:

But more info here: http://forums.quattroworld.com/s4s6/msgs/168463.phtml

[Error404]

I knew you'd have some info tucked away Dave. Good picture showing the guts of the thing. so it is just a boggo reed switch.
That Item 8 "speedo drive" must have magentic tips on the teeth then?

[UrS4boy]

I knew you'd have some info tucked away Dave. Good picture showing the guts of the thing. so it is just a boggo reed switch. That Item 8 "speedo drive" must have magentic tips on the teeth then?

Good insight on the magnets.

I just searched on 012409187C, the drive gear and came up with these two diagrams (that I will be adding to my G68 post - thanks for prompting me to add more info )

[Error404]

so by the look of it that then makes 8 impulses per revolution?

[UrS4boy]

so by the look of it that then makes 8 impulses per revolution?

That's what I get.

[Error404]

Can anyone confirm then that the sender in the OEM system / configuration generates a 5v square wave pulse as Aaron's description above?

[UrS4boy]

Tranlation of the German, not perfect but you get the idea:

How it Works

In the tacho-wheel is a 4 pole paired connectors that provide interfaces, ferrite magnet molded, there are alternately 4 North and 4 south pole in a row. The tacho-wheel is rotated so that individual magnetic field on the Reed-contact effect, is closed. As soon as the interfaces between north and south pole to the reed-contact aligned south, opens the contact.

This process is repeated per revolution of the tacho-wheel 8 times. The speed of the Tacho-Gebers reaches the electronics of the speedometer and is the speed and distance with the help of a IC and a stepper motor processed and reinforced.

Reed-contact

The reed-contact is a tongue contact. It is for the protection against pollution, moisture and corrosion in a gas-tight glass melted down. In the glass tube is located a shielding gas. The closing and opening the contact is made by magnetic force.

[prj]

I want to put a sensor onto the input shaft of my 01E...
Still wondering if I could fit one somewhere.

[AndyP]

Can anyone confirm then that the sender in the OEM system / configuration generates a 5v square wave pulse as Aaron's description above?

I can't help you I'm afraid, but I'm curious as to what you're up to