On Mon, 05 Feb 2018 13:11:50 -0500, "(PeteCresswell)"
wrote:

Per dpb:
The problem with inexpensive bulb thermometers is that the capillary
dimension has to be exceedingly precise in order to control both the
linearity and scaling and doing that drives the price up

What type would you say is the least prone to inaccuracy?

Bi-metallic spring?

Digital?

I have played around with digital sensors and a Raspberry PI and the accuracy
was pretty bad.... but maybe that's just el-cheapo sensors and/or my
programming approach...

Mercury filled bulb type seem to be the gold standard that are used to
calibrate the others but these are tested, lab grade, not chinese bulk
goods.
Paying more may not guarantee quality but paying less certainly says
the quality is going to be a crap shoot because there is less quality
control. The ice water deal is a good single point calibration but use
distilled water for the ice and the water bath. Any dissolved salts
will skew the results. We see that when we are calibrating our
instruments. A tap water ice bath will typically be a little colder
here in Florida but we have salt water intrusion in most of our
aquifers. You might be fine up in those places where ther water comes
from springs that are unaffected by mineral deposits or the sea.