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Topic: Multiplexing a Thermocouple Input (Read 14744 times) previous topic - next topic


FWIW, as promised, I was able to calculate the S/H coefficients for the Thermoworks probes.  I haven't done extensive testing, but seems to be accurate to a few degrees F using a 10K resistor divider.  I haven't yet calculated if that's the most optimal value yet, but it seems to provide a reasonable starting point.  I created a new threads so hopefully it's easier for others to find in the future. 



Mar 14, 2011, 08:34 am Last Edit: Mar 14, 2011, 10:19 am by Drunk_J Reason: 1
I'm a little late on the conversation, but was wondering if you had seen this project (link below).  Anyway, thought it may help.


Or this if you're still looking at thermocouples.

Thermocouple source (type K) - http://www.thebbqguru.com/products/Meat-Probe-%28DigiQ%2C-CyberQ%29.html



Wasn't aware of those projects, thanks for the links!  Looks like quite a few people have tried to create various smoker datalogger & controller solutions. One thing that other's may be interested in are the S/H coefficents for the Maverick thermistors which I found at the very bottom of this page: http://hruska.us/tempmon/BBQ_Controller.pde

A = 2.3067434E-4
B = 2.3696596E-4;
C = 1.2636414E-7;

The author is using a 22.2K resistor as a voltage divider.

I haven't verified how good these numbers are, but sounds like a lot of people have Maverick probes already and may find those numbers useful.


No problem.  BTW, I just ordered the TC4 shield and LCD board from the thermocouple link I listed above.  I already have numerous thermocouples from BBQ Guru folks (they are plenty accurate), so decided to take that approach.  Though I will have to change the term blocks on shield to jacks to match probes (prefer plug in option).  They also have a software project site for their shields - http://code.google.com/p/tc4-shield/ .  The shield was developed for coffee roasters.  Hoping it will not be a far stretch to adapt to a smoker.




Thanks for the S/H coefficients. I'm still working on the MAX6675 ADG609N combination as time allows. I've almost got it wired up and ready to test. When I get done with that I'll test the Maverick thermocouples again. They would be more cost effective than the thermocouples and simpler to wire up.


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