Pszemol wrote:
Looking at the scale of mine refractometer with divisions for 34 and 35 ppt so close
to each other and comparing wide scale of swing arm with a centimeter between 34 and 36
is it hard to believe refractometers are "much more accurate"... But I will take your word.

Also, would you agree that Coralife statement of +/-0.001 SG accuracy of their
DEEP SIX is not true if you say +/- 1ppt refractometer is "much more accurate"?

A measurement tool is more PRECISE if it can measure to a greater number
of significant digits. The Deep Six is a more precise measuring device.

A measurement tool is more ACCURATE if it can come closer to the true
value of whatever it is you're measuring. The refractometer is more
accurate.

From this, hopefully it's clear that it does no good to be more precise
if the instrument is not accurate. We use refractometers because they
are fairly accurate. Unfortunately, they are not very precise.

Eric