[Homeroast] Sunbeam Vac pot tuning: a simple solution

raymanowen at gmail.com raymanowen at gmail.com
Thu Apr 15 01:22:49 CDT 2010


You say " The result is water at 200-203 F each time in the upper globe and
very nice coffee."

I am sorely tempted to ignore the political scene, international terrorism
and posit that the temperature was not the "200-203 F" you imagine. That's
1.5% precision- Not with a meat thermometer that can't be calibrated or read
that closely and improperly installed.  A frangible device, poorly installed
with toxic contents sounds like a sequel to Poe's *The Pit and the Pendulum*
.

Without instigating quarrels, flaming, etc,- if the result already is "very
nice coffee," what more do you want?  For a certainty, if you keep tinkering
your results will change.  Some better, some worse.  Keep notes.  Small
increments in grind size, along with time and the mythical temperature
control make the brew.

Ice can exist at 30°F, 20°F, -20°F, -40° with little effect on the ice bath
temperature. Ice absorbs most heat when it melts. (32° ice --> 32° water).
It's a stable temperature regulator only at 32° F. There is no regulation at
any other temperature,

You would never use a precise Hg thermometer around food stuff, but note
that for basic research use, the proper calibration check procedure is to
fully immerse the thermometer body in the heated medium (water or oil) and
compare the 10% FS and 90%FS readings for Ø and Full Scale, against a
mercury standard thermometer. Most physical devices are non-linear and
useless at the extreme ends of their scales

Unless your thermometer is thus calibration-checked along with that of a
separate technician, the two can never duplicate each other's results, Most
people using cheap (<$100) thermometers or a bad installation, couldn't tell
the difference between 200°F and 203°F, if their life depended upon it.  If
the coffee already rates as "very nice," and you can repeat it stop talking
and start enjoying.

If you don't know anything about parallax scale errors, a digital
thermocouple readout probably won't help, given a poor initial installation.
How many grad students wanted us to instrument their projects with new
thermocouples, connectors and lead wire "for accuracy," for free. Beggy
choosers.

Cheers, Mabuhay -RayO, aka Opa!

Got Grinder?


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