Re: Stars drift with high resolution encoders


Dan Gray
 

Can you tell me the diameter of the disk for the magnetic tape?  In the spec sheet, it gives about +-0.004 mm per meter for magnetization accuracy + interpolation error .
If we know the diameter, we can figure out the arc seconds error.
We can also find the period of the interpolation if we know which readhead you have. The pole spacing is 1, 2, or 5 mm.
Dan


On Mon, Aug 23, 2021 at 3:52 AM <Joerg> <joeps@...> wrote:

Hi Dan,

 

The encoders have been discontinued but I found a link to the user manual.

http://www.enkodery.pl/download/instrukcja_obslugi_gc-mk.pdf

 

I have a pole length of 1mm and the highest resolution read head.

 

Now I made some additional tests. In all modes with activated scope encoders the drift is visible, also with tick management.

There is no large difference whether only one Az or Alt encoder have been activated or both at the same time.

When one or both scope encoder enabled the star follows a circular trail of about 3 times the star diameter. The time for a complete circle is several seconds.

What I don’t understand is the circular trail when only one encoder is enabled.

In my opinion in that case should be the trail a line if magnetization accuracy and interpolation error are blame for that.

 

Joerg

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