After 2 years of not worrying about it, I'm now eager to revisit the
subject of offset in my Brewtus. Two years ago I conducted an
experiment where I adjust the Brewtus' temp controller offset from -1
to -9 degrees while keeping the desired brew temp (the number on the
front panel of the Brewtus) fixed to 96 degrees and measuring the
resultant brew water temperature. The brew water temperature was
measured with a probe where the small bolt on the E61's brewhead would
be (I removed the bolt) and with a blind basket in the portafilter.
In this way the probe would be completely immersed in water during the
measurement.
At the time, the results of my experiment were as follows:
Expected Estimated
Boiler Temp at Temp at
Setpoint Offset Temp G/H bolt P/F
96.00 -9.00 105.00 99.00 96.78
96.00 -8.00 104.00 99.00 96.78
96.00 -7.00 103.00 99.00 96.78
96.00 -6.00 102.00 99.00 96.78
96.00 -5.00 101.00 99.00 96.78
96.00 -4.00 100.00 99.00 96.78
96.00 -3.00 99.00 97.39 95.17
96.00 -2.00 98.00 96.78 94.56
96.00 -1.00 97.00 94.17 91.94
The unfortunate part of my experiment is that I cannot make a
pressurized measurement, as I do not have a Scace or similar device.
These tests were essentially conducted at atmospheric pressure due to
the removed E61 bolt, and it is not surprising that after a certain
point (when setpoint - offset approaches 100C) that any further
adjustment of either offset or setpoint would not matter.
However that still leaves me wondering how much of a difference a
pressurized reading would make, at least at the pressures found in
actual espresso brewing, with a Scace device. Afterall I'd still
think that as the water leaves the brew boiler through the 3-way valve
to the grouphead that there is regardless a steep drop in pressure
until the pressure can be built back up again as the incoming brew
water purges out all of the air in the grouphead. And as it is this
initial volume of water that actually brews our espressos, I wonder
what is the temperature of that water under normal brewing conditions
through the range of programmed offsets (as in my experiment above)?
Would someone in this group who has a Scace device volunteer to do
such an experiment? More specifically perform a series of Scace
readings of the brew water in the grouphead at a fixed "front panel"
temperature and varying offset? What I suspect is that even under the
pressurized conditions of a Scace reading that there will be a clear
"breakpoint" whereafter changes in offset have no effect.
(With many thanks in advance to whoever might takeup the challenge!)
--
You received this message because you are subscribed to the Google Groups
"Brewtus" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/brewtus?hl=en.
