Posted Sun Apr 13, 2014, 10:48am Subject: Behmor Temperature Datalogging
There have been many threads about bean mass temperature and the near impossibility of measuring it on the Behmor 1600.
If you did get a thermocouple probe into the bean mass, you would not get an accurate reading due to the influence of the heating rods.
However, lets try something else: If you remove the top of the exhaust duct (top rear, 5 screws) you will see that the exhaust fan is small. My guess is that the airflow while roasting is minimal. In that case, the temperature of the exhaust air will be roughly proportional to the bean-mass temperature. That means that you will get a curve of approximately the right shape but the temperatures will not be accurate.
I did a roast of a nice Sumatra yesterday with a type K thermocouple (and reader) and got the curve shown below.
I went 'to cool' at exactly 3 minutes after the onset of the 1CR (because of previous experience). At that point, the heating stopped and the fan speed increased.
Now …here's the interesting thing... Even with no heat and much more cooling air, the temperature spiked up by 40F over the next 2 minutes. That is not shown on the graph (created in Danny Hall's Roastmaster App) because I hit the stop button. So, at the onset of the 2CR the roasting process REALLY goes exothermic. And the spike happened so quickly I doubt if I could have gotten (say) 30 sec of 2CR if I wanted to.
The next time I roast I will watch for the onset of that spike and go 'to cool' there. In conclusion, I can't measure bean-mass temperature, but exhaust air temp is still pretty useful.
If anyone is interested, I could point you at a very nice (low-cost) type K thermocouple which fastens with a threaded connection and a matching nut. All you have to do is drill a 5/16 hole at the end of the exhaust duct.
Posted Sun Apr 13, 2014, 1:53pm Subject: Re: Behmor Temperature Datalogging
Actually, Craig, I think not.
While roasting, I watched (on my Kill-A-Watt Meter) the afterburner coming on and the main burners cycling off/on once or twice Yet there was no equivalent up-and-down on the temperature curve. But when I went-to-cool, the spike was major. That was with only the afterburner (500w), no main burner (1000 w) and much more air.
What I need to do is find some beans I don't particularly like and roast them right into a rolling 2CR and plot the curve.
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