Re: [CAD_CAM_EDM_DRO] Linear encoder outputs

philsumser wrote:

>Greetings All
>
>Does anybody have an answer to the following problem. I have recently
>purchased some Acu-rite Turnmate scales which I intend to fit to my
>lathe and milling machine. They are about 10 years old but are brand
>new and still in their sealed packaging. My idea is to connect the
>outputs of the scales into the serial or parallel port on a PC to act
>as a DRO(I already have the software for this). The output of the
>scales is analogue differential sinusoidal quadrature phase current at
>7-18.5 micro amps into a 1Kohm load, but I need the usual 5v quad phase
>TTL signal for the computer. Does anybody know of a circuit I can build
>to effect this conversion?
>
>

What is the line pitch resolution of these scales? Simple hardware will
just compare
the + signal against the - signal, and give one count as each signal passes
through the midpoint. This will give a readout resolution that is 4
times the
line pitch of the scale. If these scales were designed for use with an
interpolator,
they may have very coarse resolution, like 100 uM, which will work out to
a DRO resolution of 25 uM. Since you are in New Zealand, you will
probably use
them in mm mode, so maybe that will be enough. It would probably be
unsuitable
in the US, as the conversion to inches would cause it to skip many .001"
values.

Jon