Gear Tooth Sensor Air Gap

[djb]

Does anyone know of a gear tooth sensor that is capable of detecting a target with a 2-3" air gap? Are there ways to compensate for this air gap? Are there any other types of sensors capable of detecting with an air gap of this size?

As an aside, does anyone know anything about magnetic fluids and a possible application with hall effect sensors?

 

[Optikon]

Does anyone know of a gear tooth sensor that is capable of detecting a target with a 2-3" air gap? Are there ways to compensate for this air gap? Are there any other types of sensors capable of detecting with an air gap of this size?

As an aside, does anyone know anything about magnetic fluids and a possible application with hall effect sensors?

Hall effect sensor might get to that range with enough sensitivity in the detector circuit.

 

[zevon8]

Allegro makes several hall-effect sensors that probably do what you need. Using a standard magent/coil pickup over large gaps is usually easier with larger, wider spaced rotating objects. I have done this on universal joint spiders, where there are only 4 lobes, but being large masses of metal widely spaced, the signal was easier to amplify and filter to a clean signal.

 

[Russlk]

The 2 - 3" spacing of the sensor is not a problem; the problem lies in the spacing and height of the gear teeth. If the tooth spacing is 1/2 inch or less, it will take a complex circuit to make it work. If the gear teeth are spaced 3 inches and are 3 inches high, it is simple. So, why not make the gear bigger?

 

[JimB]

Why a 2 to 3" air gap?
Is it not possible to get the sensor nearer to the gear?

JimB

 

[djb]

No, its not possible to get closer to the gear. If it were as simple as that, I would have done it.

 

[JimB]

I was hoping that you would explain why its not possible to get any closer to the gear wheel :?:

If a magnetic sensor cant get any closer, it it possible to use an IR source which shines through the teeth of the gear wheel on to a IR detector?

JmB