This is a picture of the controller board wich is located on the bottom of the MES. I had to scrap off all the protective sealant so that i could read the board better. Mabe this will help.These MESs are kind of disappointing. It seems that they're not very accurate for whatever reason. I have not had the controller apart. I just put my smoker together and started using it right away. I will take it apart and see what I can find out from looking at things. I would not make any guess as to whether the controllers or the probes are to blame for the strange deviations we're seeing in these units.
First....great write up with some very interesting analysis..!!
As to the temperature variance....could it be due to the fact that they might not be linearizing the thermocouple millivolts? When we bring in a TC as a direct millivolt reading, we have to use a 2 or 3rd order equation.....if you dont, then you get non-linearity in your input readding. Temperature controllers all do this normally, but maybe they arent compensating for the non-linearity.
Has anyone looked at the control board to see what they are using for the input probe measurement...? Would be interesting to see what reading they are expecting, and if it is a millivolt signal....then to redirect the probe into a arduino or other chip to compensate for the variances.....Just a thought.
I have an analog MES 30 that I got for $115 at Sports Academy, and I used a Omega Temperature Controller with a K-type TC stuck in the rear air slot. I used a SSR with a female plug attached to the controller, and I just set the rotary dial to 100% and let the controller do the action. I found, as you stated earlier in one of your comments, that PID control was too tight, and wouldnt allow smoke, but setting it to On-Off with about 3 degrees of Hysteresis gives great temperature control with LOTS of smoke.
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