Linear encoder resolution

[Inskeep]

Hello,
I have been researching linear scales for true closed loop system.
When I was buying linear encoders in the past resolution was in pulses per inch (PPI)
My question is a 5um scale 5um per mm or what? Most all the scales I've looked at just are in um.
Am I having a senior moment or am I just over thinking it.
Thanks
Ken

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[Al_The_Man]

5µm is per graduation of the scale, or the resolution.
Al.

[Jim Dawson]

5 um = 5 micron = 5080 PPI. About 0.0002 inch / pulse. If your motion card will handle it, I would go with 1 micron magnetic scales. That's what I have on all of my machines.

[Inskeep]

Thanks for your reply
I changed my search terms and realized that is actually the pitch.
Just needed to hear from someone else.
Thanks you guys

[fuelbrain]

I believe it would be just 5um. Micrometer is it's own unit, it doesn't need another unit attached to it. This means you will get 1 count every 5um. So you will have one encoder count every 0.00019685"

[Al_The_Man]

And if fed through a differential driver you will obtain 4x the resolution. (5µm/4).
AM26C31.
Al.

[rodw]

I believe it would be just 5um. Micrometer is it's own unit, it doesn't need another unit attached to it. This means you will get 1 count every 5um. So you will have one encoder count every 0.00019685"

The unit is a micron (one millionth of a metre or 0.001mm). Metric makes it so much easier as a 5 micron scale has a resolution of 0.005mm. I've used 1 micron scales on both of my machines as they were only about $10 more at the time so they have a resolution of 0.001 mm