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Am I doing something stupid TC4C+Artisan
therabidweasel
Top  #26 Print Post
Posted on 11/03/2014 1:43 AM
Hopefully not digging the hole any deeper, but I never thought there was a problem with the Artisan software per se. My theory was maybe the units switch was accomplished by toggling a state without maybe checking the current state or some other mechanism that might allow it to get out of sync in rare instances. I did not mean to cast aspersions on the software, which is freaking awesome and has better support than most paid software. It reminds me of a quote of Ben Franklin that was something like: teach a man to shave and keep his razor in order and he'll have a lifetime enjoying shaving on his on schedule and to his liking and benefit. Thanks for helping all of us "shave" Artisan team.

I'm wondering about the results I was getting by querying through the Arduino serial monitor. I think maybe that was because by shutting artisan off to open the port I was also shutting the heater off. I know the heater current was affecting the grounding because I can see it in my curves. I don't really understand the mechanism though because the PC and roaster were on separate circuits and the roaster chassis isn't even connected to anything. . .not to mention I have ungrounded friggin probes. I'd welcome any theories because I am missing something there.
 
JimG
Top  #27 Print Post
Posted on 11/03/2014 9:21 AM
I can't pinpoint a cause-and-effect relationship. But I know from experience that there is a high correlation between shielded probes and problems with the TC4 hardware.

The chip that reads the thermocouple signal is pretty sensitive -- remember we are looking for differences measured in microvolts in a thermocouple signal that rarely gets above 10mV. Also, when set to its highest resolution mode, the input impedance of the chip is not as high as I would like it to be (a tradeoff).

So anything that messes with the potential difference between the GND plane on the TC4 board and the tip of the thermocouple can mess up your readings.

Something about the shielding on the probes seems to mess with this potential. I can't put my finger on what it is, but like I said above, there is a very high correlation between shielded probes and problems!

Jim
 
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therabidweasel
Top  #28 Print Post
Posted on 11/03/2014 10:45 AM
Something just seems wrong about a "shield" causing problems, doesn't it? I'm glad i payed omega top dollar for them. It works now though, and it's an easy fix I reckon. It's also something to ponder over an ale 8!
 
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