Spehro Pefhany may or may not have intoned:
On Fri, 9 Oct 2009 15:00:10 +0100, AdeV
wrote:

Recently, I bought a 24" digital scale from Chronos, which I fitted to
the Z axis of my machine. It looks very similar to this one, only
longer:

http://www.chronos.ltd.uk/acatalog/info_SGU___.html


I'm somewhat annoyed to discover it has a 0.004" error in every 0.100"
of travel! Is this normal for this kind of scale, or have I got a duff
one?

Could this be a machine with metric lead screws and fudged imperial
dials?

I did wonder that, what with the other axes being metric; but according
to both the depth micrometer & the dial caliper, it's definitely an
imperial leadscrew on the Z-axis...

A large fixed percentage error would be difficult to achieve given the
way they are made inside.

On the other hand, it IS possible for the machine to be interpreting
each division incorrectly... I've seen discussion of Heidenhain DROs
having a scale adjustment inside, which allows you to adjust out any
scale error. I can't see anything similar with the Chronos unit, and it
came without instructions of any kind, so I'm a bit in the dark
really...

I haven't yet verified it has the same error when reading metric, but I
guess that's the next step.

--
Cheers!
Ade.