HomeRoast Digest

Topic: Thermocouple Placement (6 msgs / 164 lines)
1) From: Dennis Parham
Well... I now have a digital thermometer with K type thermocouple... 
and trying to decide where to install it in either my air Original 
poppery I .. I just ordered a 10" oil lamp cylinder thanks to Michael 
Dhabolt...(THANKS MIKE!!) and Im going to make a new case for it all 
and controls.... but I have been taking temp readings with the probe 
and it is sporadic at best...  what am I actually measuring in popper 
chamber?? obviously with it dangling in there not the bean mass 
temp...as the second I turn off popper.. the temp drops 100 no matter =
how deep I put it in there...
Dennis Parham

2) From: Edward Spiegel
At 3:27 PM -0600 3/28/05, Dennis Parham wrote:
 in there not the bean mass temp...as the second I turn off popper.. the=
 temp drops 100 no matter how deep I put it in there...
Where do you have it placed? Is is a bead or a wand? I lower mine on a=
 bamboo skewer so that it is about 2/3 of the they up in the bean mass and=
 away from the vents (if the thermocouple is too close to the vents or the=
 edge, you will be heavily influenced by the canister temp and air flow). My=
 readings (when I was still using the thermometer) were quite consistent and=
 there was minimal temp drop. Mine has a bead-type thermocouple. A wand will=
 be more influenced by non-bean temp. The bead thermocouple is so small that=
 if you have it placed right it will mostly be influenced by the beans in=
 contact with it.
I stopped using the thermometer during roasting when my nose became=
 better-tuned to the smell of the smoke at my preferred roast stage. I found=
 that the thermometer was no longer necessary.
Anyway, that's my .02,

3) From: petzul
I pushed the TC through a thin piece of copper tubing to protect it from 
flexing. The stuff for ice maker hook up is fine.
That way you can place it in different positions and clip it to the side 
of the chamber from the top to hold it in place.
For my Turbo Beast I pushed it through the hollow shaft of a worn out 
deep fat turkey fryer thermometer. This is SS and even thinner!
I felt that moving all around all the time would cause it to fail quicker.
Hope this helps,
Dennis Parham wrote:

4) From: Andy Thomas
--- Dennis Parham  wrote:
|     |/ 
|     | <-drill hole for TC
|  *  | <-bead at surface of green beans
This is what has worked for me: I drilled a hole in
the plastic part of the chamber of P1, at an angle so
the bead is at about the top center of the green
beans. As the beans expand, the bead will end up a bit
below the surface. You are measuring the air temp at
the point of the bead. Temp probably varies quite a
bit within the roast chamber, so you want to keep the
probe steady in the same spot thoughout the roast.
It is not a perfect solution. After all, it measures
only the air temp, which will vary more than bean
temp. But it still gives something to work from.
Hope this helps.
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5) From: Philip Keleshian
I have a section of steel tubing which passes thru the lid of my Z&D.  =
The tubing directs the thermocouple probe to the bean mass.  I used a =
similar arrangement in my HWP.  Here is a link to the picture of the =
modified lid:http://www.coffeegeek.com/forums/coffee/homeroast/29149?Page=2I had to use steel on the Z&D (I had tried copper) because I lost too =
much heat with the copper tubing. Copper worked fine on the HWP. 
My guess is that copper will work well in a true fluid bed roaster where =
you have heat to waste.  If getting enough heat is an issue (such as in =
a Z&D) avoid copper or aluminum.

6) From: David B. Westebbe
but I have been taking temp readings with the probe 
You are measuring some kind of average of the air temp and the bean
You cannot know what the proportions are, and they will change

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