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Topic: Roast Temperature Sensing (3 msgs / 63 lines)
1) From: Ben Treichel
Hey all,
I'm looking for fact and empirical data on sensing the bean temperature 
during roasting. Is a single thermocouple sitting within the 'float' 
area of the beans accurate enough? I believe a HWP does it this way, 
however I have never seen one. Or does one need to sense air temp below 
and above the beans, and imply bean temp by the difference between the 
two ( bigger delta T means the beans are still absorb a lot of heat). Or 
does the measurement need an IR type surface temperature measurement.? 
However this sensor is ~ 10X the cost of a thermocouple.
While a single thermocouple 'may not' report bean temperature 
accurately, my suspicion is that it will give you repeatable roasts at 
the same temperature.
Ben
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2) From: Dan Bollinger
<Snip>
Ben, It is if the hot roasting air isn't percolating through the beans and
hitting the sensor.  Most hot-air roasters are 'single chamber' designs and
sensing bean temperature (more accurately called bean environment
temperature) is very difficult.  That's why some mfgrs. have gone to two
chamber machines.
<Snip>
Nope, the HWP senses heater output, just before it enters the roasting
chamber.  You can see the thermistor on the base unit.
<Snip>
I think it will give you some good information to add to your other inputs,
time, smell, appearance and cracks.  Dan
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3) From: Mike McGinness
From: "Ben Treichel" 
 While a single thermocouple 'may not' report bean
temperature
<Snip>
While no facts or empirical data on accuracy or 'best' positioning, I 100%
agree, from a 100 or so roasts using bean temp', that much more repeatable
roasts is indeed attainable. In the vain of temp' measurement placement
variation, I was chatting with my friend Gus at Pele Plantations a few
months ago. He'd just got his new, bigger, Sivetz installed and operational.
Since I knew he roasted by temp using a thermometer on his smaller Sivetz, I
asked how they compared. The larger needed 30f lower for the same roast
result. I didn't ask details on placement etc. or time of roasts or whether
just judging the roast color or grind color comparison etc... Roasting
wasn't the focus of our conversation. Figured I'd see for myself when we
visit during the Kona Festival in November;-)
MM;-)
Variable Variac Rockin' Rosto Roasting in Vancouver, WA USA
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