Re: [CAD_CAM_EDM_DRO] Subject: Re: Glass scale problem

tig415 wrote:

>The interesting thing is for about ten minutes after I wipe the bad
>section of the scale with alcohol it is dead on accurate. After
>that it starts missing more and more counts until the whole section
>(.176") skips. The DRO flips the last number back and fourth but
>doesn't count I'm sure the alcohol leaves a film that's changing the
>refraction of the light coming through the scale.
>I'm going to take a closer look at the head and also investigate
>what's available in the lens coating solutions. I think the CD stuff
>sounds promising.
>
>

Well, I think the alcohol is a red herring. My guess is that if you
disassemble and reassemble it without cleaning anything, the same
thing will happen. Meaning that it is the act of disassembling it that
puts something back into alignment for a while. (I could be wrong
on this, of course.) The flipping one digit only sounds like only one
of the
quadrature channels is changing, the other is constant through that
bad section.

One other possibility is the LED has weakened, and that it has just
enough output to work OK when cold, but after heating up for 10
minutes, it is too weak for the DRO to work on one section of the
scale that is a little off for some reason (dirt, scratches on the chrome,
etc.)

If the LED is weak, you could change the series resistor to increase the
output a little. Or, you could get a new IR LED, if it is a standard
package type device.

There may also be adjustments for the sensor sensitivity on the head.
You might adjust them a little and see if the problem clears up.

Jon