Re: i-roast 2 profile adjustments for ambient temperature changes
- From: bwilson4use@xxxxxxxxxxx (Bob Wilson)
- Date: Sat, 24 Jun 2006 19:49:48 -0500
diab0lus <r0cketscientist@xxxxxxxxxxx> wrote:
THANK YOU!!
I have been collecting temperature data for my roasts with a
temperature probe inserted through a small hole drilled in the top of
my i-roast 2. I have figured out a formula to predict, within a
certain degree of accurracy, the difference between the average
measured in-the-bean temperature (recorded every 15 seconds) of the
i-roast 2 and the average programmed temperature (every 15 seconds) as
they relate to the ambient temperature.
The temperature ranges that were used while collecting this data range
from between 50 F and 85 F. The formula predicts that the average
programmed temperature equals the average measured temperature at about
30 F. I recorded the measured temperature every 15 seconds throughout
the duration of each roast. All of my profiles are of the ramp-up
variety. I don't drop the temperature at any stage in my profiles and
don't know if this will work with those types of profiles.
Here is the formula to calculate the amount that the average measured
temp should exceed average programmed temp (F) as a percentage:
(ambient temp - 30)/1100
So if it is 90 F today, the % over average programmed temp will be
about 5.5%. You can use these figures to adjust your roast profiles
accordingly.
If you want to input your average programmed temp into the formula to
find out your average roast temp use:
([(ambient temp - 30)/1100]+1) * Average programmed temp = Average
roast temp
I have a first generation iRoast and had noticed there was no
compensation for ambient temperature. But I didn't figure out the
correction curve. This is great!
I'll put together an excel spreadsheet for 5 degree increments from
40-90 and finally get back into the sweet spot, consistently.
------------------
On another note, I have observed faily consistently that the i-roast 2
will exceed its programmed temperature by about 19%. So I have been
programming the last stage on the i-roast by using this formula:
Desired Roast Temperature / 1.19 = Programmed Temperature
Using this approach requires the stage to be at least a minute long.
It shouldn't be preceded by a big jump in temperature - it needs time
to biuld up heat. What I have observed is the approximate maximum that
it will exceed the programmed temp.
Using these two approaches I have been able to get about a 15 minute
roast at the temperature I want with a nice ramp-up temperature curve
in some different ambient conditions. If my wife let me roast in the
house, I wouldn't need to go through all of this trouble.
I am interested to hear if these formulae work for anyone else using an
i-roast 2. I have read that performance is inconsistent from unit to
unit.
I'll let you know in a month or so. I typically roast once per week and
it will take a couple of samples to tell. I had been stopped by 'heat
shrink' on my temperature probe but I've got a replacement that is
stainless steel enclosed.
Bob Wilson
.
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