HomeRoast Digest


Topic: More Digital Thermometer (long) (66 lines)
1) From: Rick Farris
I posted earlier this week about my experiments with the $20 Digital
ThermoMeter (DTM) from Circuit Specialists.  I think I mentioned that it was
hard to hold the probe in exactly the right position.  Well, what was *hard*
for one batch was a killer tonight when I tried roasting six batches.
The thermocouple wire is just stiff enough that any motion of the meter or
wire on the outside of the roaster is enough to cause wild variations of the
position inside.  It is a full-time job trying to keep the probe placed
correctly, let alone make any roasting notes.  If you've ever tried fishing
a coat hanger into your car to unlock it you know exactly what I mean.  And
because the whole idea of the DTM was to keep me from getting a crick in my
neck from craning to look at the analog dial thermometer (ATM), I was not a
happy camper.
As I mentioned, I roast with a Home Innovations (Hearthware) Precision
(HIP).  After my roasting session (Kenya Karumandi -- I've got about 10
pounds of Kenya I *don't* like, I'm hoping this will be the one!) I took my
roasting chamber apart and looked for a way to mount a thermocouple.
Because I like to toss the roasting chamber in the dishwasher, I didn't want
the thermocouple permanently attached to the roaster.
I don't know how to drill glass, so that ruled out drilling a small
(~3/32")hole in the side of the roasting chamber and simply sliding the
thermocouple in while roasting.  That would also leave the problem of
sealing around the edges of the thermocouple wire.  I figured I could prolly
pack it with monkey shi^H^Htuff, but I'd still have the problem of the
thermocouple moving all over the place if I brushed the wire.
It occurred to me, though, that if I could somehow mount a small clip -- it
needs to be small or else it will interfere with the fluid bed -- on the
floor of the roast chamber at about the right place, I could simply feed the
thermocouple wire in through the existing vent holes in the top and clip it
into the ... well ... clip.
The roast chamber on the HIP is held together by three screws that are
accessed from the bottom of the chamber.  Once I removed the screws, I found
a shield, a gasket, the roast chamber bottom (metal) floor and another
gasket.  It looks like it will be pretty easy to drill a hole in the roast
chamber bottom, use a screw to attach some kind of clip, and put the whole
thing back together.  I'll need to make sure I use a short screw that will
fit in the small space between the shield and the roast chamber bottom.
Now that I've identified a solution, I'm sitting here scratching my head
over an implementation.  The hardware I'm looking at is pretty small -- on
the order of ought-80 -- and I'm not sure where I can find a selection to
pick through.  I'm thinking of a little tiny angle bracket.
I suppose I'd better consider the fact that this is a high heat/vibration
environment and plan on loctiting it together.  Does anyone know if that
stuff gives off fumes after it's cured?  Is there special loctite for high
temperature work?
-- Rick
P.S. One thing to consider when you're coming up with your scheme for
mounting *your* thermometer: Be really careful about how much you interfere
with the fluid bed.  At one point tonight I tried wrapping the thermocouple
lead around a big nut and tossing it into the roasting chamber.  The nut
created a big enough "shadow" behind it that maybe 1/8 of the beans weren't
moving around! [RF]
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