Thane Heins Perepiteia.

[polarbreeze]

"By Faraday's law, the voltage on the coil is the rate of change of flux through the coil.  It doesn't matter one bit that the flux is confined to the shaft.
That's why transformers work, eh?"
Cheers,Mr. Entropy

...

IF YOU LOOK AT THE CROSS SECTION OF THE DRIVE SHAFT IT WILL HAVE POLARITIES AS SHOWN BELOW:

  N  pole
O  - Drive Shaft
  S pole

EVEN IF YOU COULD CREATE A BRUSHED SYSTEM FOR READING YOUR DRIVE SHAFT COIL OUTPUT - THERE WOULD BE NO OUTPUT BECAUSE THE TOP HALF OF THE COIL'S INDUCED CURRENT WOULD BE CANCELLED BY THE BOTTOM HALF.

THE DRIVE SHAFT FLUX DOES NOT TRAVEL INTO AND OUT OF THE "PAGE" O AS IT WOULD IN A TRANSFORMER - BUT RATHER IT IS FLIPPING...

Thane

1. I don't think you can say what the field looks like unless you measure it.

2. I don't think you need a brushed system: the coil can be static and have the shaft rotating within it.

PB

[polarbreeze]

A stationary coil over the rotating shaft would give you changes in the magnetic field...
But it would not give you the intensity of the magnetic field.

It would be quite easy to calibrate the sense coil against a known core with a known field. That would allow absolute measurements of field to be made.
PB

[OilBarren]

"By Faraday's law, the voltage on the coil is the rate of change of flux through the coil.  It doesn't matter one bit that the flux is confined to the shaft.
That's why transformers work, eh?"
Cheers,Mr. Entropy

...

IF YOU LOOK AT THE CROSS SECTION OF THE DRIVE SHAFT IT WILL HAVE POLARITIES AS SHOWN BELOW:

  N  pole
O  - Drive Shaft
  S pole

EVEN IF YOU COULD CREATE A BRUSHED SYSTEM FOR READING YOUR DRIVE SHAFT COIL OUTPUT - THERE WOULD BE NO OUTPUT BECAUSE THE TOP HALF OF THE COIL'S INDUCED CURRENT WOULD BE CANCELLED BY THE BOTTOM HALF.

THE DRIVE SHAFT FLUX DOES NOT TRAVEL INTO AND OUT OF THE "PAGE" O AS IT WOULD IN A TRANSFORMER - BUT RATHER IT IS FLIPPING...

Thane

1. I don't think you can say what the field looks like unless you measure it.

2. I don't think you need a brushed system: the coil can be static and have the shaft rotating within it.

PB

GREAT! THANKS FOR THE OFFER!
JUST LET ME KNOW WHEN YOU WANT TO COME TO THE LAB AND GET STARTED?

AETHER22 CAN PB COME TO YOUR HOUSE FOR TESTING INSTEAD - IT'S WARMER?

Thane

[OilBarren]

A stationary coil over the rotating shaft would give you changes in the magnetic field...
But it would not give you the intensity of the magnetic field.

It would be quite easy to calibrate the sense coil against a known core with a known field. That would allow absolute measurements of field to be made.
PB

GREAT! THANKS FOR THE OFFER!
JUST LET ME KNOW WHEN YOU WANT TO COME TO THE LAB AND GET STARTED?

OH FORGET IT!

WHEN CAN I SET UP THE PROTOTYPE AT YOUR HOUSE?

Thane

[polarbreeze]

"Put a coil round it."PB

THE MAGNETIC FIELDS ARE CONTAINED WITHIN THE FERROMAGNETIC MATERIAL (UNLIKE COPPER CURRENT BEARING WIRE) SO WHAT WILL THE COIL READ OTHER THAN STRAY FIELDS?

Thane

The alternating magnetic field in the shaft will induce a current in the coil. That's how a transformer works.

I DON'T KNOW ANYTHING AT ALL ABOUT TRANSFORMER OPERATION?
I AM WILLING TO LEARN THOUGH.
MAYBE SOMEDAY I WILL FIGURE OUT WHAT IS GOING ON HERE:
http://ca.youtube.com/watch?v=BJqnfR3B4oc

Thane

It's not complicated, Thane. Just a static coil around the shaft is all you need for a sensor. No involved transformer theory required.
PB