After noticing the discrepancy between Steve's and my reading, I thought it would be good to confirm the thermocouple is in good condition. I also noticed there's some waviness in the logged measurements, so I went to Jaycar and got a new bare K thermocouple.
With the new thermocouple placed in a similar fashion, the reading was completely different.
This was before with the original thermocouple:
- 75 colombia honey piedras 60g_19-10-27_1219.jpg (88.5 KiB) Viewed 2057 times
- new probe 78 Colombia Harrera 60g_19-10-27_1404.jpg (90.12 KiB) Viewed 2057 times
- 80 Colombia Harrera 50g_19-10-27_1430.jpg (95.9 KiB) Viewed 2057 times
The MET for both batch size (50g and 100g) actually went closer to 260-265 deg C, similar to what Steve was observing. In fact, there was not so much difference in terms of MET for both the roasts. Looks like my previous conclusion/hypothesis was probably all wrong and was based on a dodgy probe.
I have no idea why, but it looks like my old thermocouple is probably on its way out (it's a good probe too, an ultra-thin probe from Omega). Unexpectedly, it behaved so differently and consistently when I had different batch size, thus leading me to an incorrect direction (sorry!
).That brings me back to square one then (in terms of an explanation for better result with smaller load size). Perhaps the reason that the larger load was worse was due to insufficient mixing/rolling(?) (have I ever learned from my mistake to not easily make a speculation??
)