Yeah, I find the Vertex ones are pretty bad for wandering.

I calibrate my vertex when I think about it which is once every month or so.

you wouldn't think that a name like 'vertex' would offer a product which sounds more touchy than others?

Perhaps I'm just too rough on precision tools - but if I calibrate mine (I use the solution as well) and then set it down on the table a couple times (about as diligent if it was a glass of water, so not too gentle, not too rough) you might be surprised to find that it will change on you.

I usually have to calibrate the unit twice, first time could have left over residue from previous testing on the glass. Second is a for sure check - and as well as the tank water, check twice or even three times, trying not to set it down or bump it into anything (I usually just dip the entire end of the Ref. into the tank)

Never.. Every once in a while o check it with RO. Never rally seems to change calibration on me

I checked mine a few times initially, but it never changed, so have not checked it for at least a year now. Maybe I should...

Never....I haven't checked salinity in years.

For those of you who do check, what do you use to calibrate? Here in PG we don't have a source of SW supplies.

this is looking like a new years resolution i can handle...

I've been calibrating my Sybon annually for a few years with calibration solution from J&L. It generally doesn't change by much unless I bump or drop it.

Looks like I'm in the market for a new refractometer. Suggestions?

Sybon.