Re: [CAD_CAM_EDM_DRO] Re: Inductsyn
Posted by
Jon Elson
on 2000-03-17 11:33:46 UTC
"Arne Chr. Jorgensen" wrote:
most important
thing that controls resolution. I don't know how you could possibly do
this accurately
enough with manual techniques. Etching a board would be much more
likely to give
good results. Probably, these things are sitting in a heap at some
scrapyard, somewhere.
Actually, the most likely way to make a good DRO is to find some old
Hilger & Watts
measuring gratings, and build an optical DRO from that. I have some
small pieces of
this stuff, and what you do is put a lamp behind the scale, and use a
small part of the
grating, tilted slightly with respect to the scale, to throw the grating
pitch off a little.
Then, you find the right spots behind the small tilted grating that
gives the correct
90 degree quadrature relationship. I worked on a 5 uInch electronic
dial test
indicator that worked this way. (That is, full scale was 5 uInch, small
divisions
were .5 u" or so.)
There must be lots of old glass scale DROs that could be rebuilt with
new electronics.
Jon
>Try http://products.analog.com/products/info.asp?product=AD2S80A
> >> It is not sensitive to voltage, but phase.
>
> >No, the amplitude varies sinusoidally with position, and the phase
> flips
> >as the signal goes
> >through the zero. You need the amplitude of both pickups to
> >interpolate, because the
> >winding pitch (equivalnt to the grating pitch on an optical encoder)
> is
> >fairly coarse.
>
> Well, - yes and no :)
>
> We don't have to debate this - my point was that the linear strip,
> or primary, is not critical to make. This is not sensitive to voltage
> drops
> along the "strip" or stability of the voltage source.
>
> I think you focus on the end part of the sensor electronics, and that
> is
> something else.
>
> Thanks for the info about the datasheets. If I come across them, I'll
> have a
> look,
> but it is very clear that you know what I am talking about, so -Well, the precision with which the wires are placed on the spar is the
> what
> is your verdict ?
most important
thing that controls resolution. I don't know how you could possibly do
this accurately
enough with manual techniques. Etching a board would be much more
likely to give
good results. Probably, these things are sitting in a heap at some
scrapyard, somewhere.
> Do you think this could be a candidate for a DIY DRO ?When you see the prices of the chips, you may start searching, again.
Actually, the most likely way to make a good DRO is to find some old
Hilger & Watts
measuring gratings, and build an optical DRO from that. I have some
small pieces of
this stuff, and what you do is put a lamp behind the scale, and use a
small part of the
grating, tilted slightly with respect to the scale, to throw the grating
pitch off a little.
Then, you find the right spots behind the small tilted grating that
gives the correct
90 degree quadrature relationship. I worked on a 5 uInch electronic
dial test
indicator that worked this way. (That is, full scale was 5 uInch, small
divisions
were .5 u" or so.)
There must be lots of old glass scale DROs that could be rebuilt with
new electronics.
Jon