Thanks for the prompt reply. After the holiday I will setup a test rig
with scope to see the signals.
I will report the results on the group. 

> -----Oorspronkelijk bericht-----
> Van: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
> Namens apptech
> Verzonden: zondag 28 december 2008 14:42
> Aan: Microcontroller discussion list - Public.
> Onderwerp: Re: [PIC] Debonce code for HALL device
> 
> >> For a project I am using a 16F685 and two HALL sensors as 
> a indexing 
> >> and station sensor device.
> >> I know that the TLE4905L device
> >
> > http://www.micropik.com/PDF/TLE4935L.pdf
> >
> >> has a logical output but would it be
> >> necessary to include some debounce code in the routines.
> 
> > To debounce what ? What would be bouncing ?
> 
> Hall devices do not have bounce behaviour within the IC 
> switch itself *BUT* there may still be mechanical variations 
> in what is being sensed which drive the sensor backwards and 
> forwards past its trigger point and effectively cause 
> "bouncing". This could occur eg on a rotating disk if there 
> is vibration present.
> 
> Generally magnetic sensors will exhibit a degree of inherent 
> hysteresis due to the properties of the magnetic circuit, and 
> will also often have inbuilt explicit hysteresis as well. As 
> Jan-Erik notes, the IC cited apparently has this feature.
> 
> > Note that the HALL sensor has an internal ST stage before 
> the output 
> > driver.
> 
> Accordingly, deboune would be required only in extremely 
> mechanically noisy cases. Try it in a worst case situation, 
> or analyse the field variations that you expect to be 
> present, and see if debounce seems necessary.
> 
> 
> 
>             Russell 
> 
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