I have the JLD612 and the PT100 thermocouple (http://www.lightobject.com/6ft-PT-100-P ... -P218.aspx) set up with the two blue contacts up to 9 and 10 and the red contact set to 8. This is in a sous vide circuit with an SSR and heating coils. I've attached one of the blue leads to the shielding to stop the fluctuation problem, and the control circuit seems to be working well. However, the actual output of the temperature is inaccurate.
I several good-quality kitchen thermometers that I trust, and I have been using them to calibrate the JLD612, which gave me readings that were ~3 degrees C too low in the warm water. To fix this, I set the offset parameter based on the difference between the JLD612 and my thermometers, and now in ~60C water the readings are very near identical.
However, when I take the probes out and put them in colder tap water (and wait for everything to equilibrate) the JLD612 reads 17.4C and the kitchen thermometer reads 18.8C. At ~55C, they're about .5C off.
This means that either the error in the JLD612/PT100 setup is nonlinear, or I'm doing something wrong in the calibration or setup. Do I need an actual external resistor? As it stands now, I'm nervous about the accuracy of the JLD612/PT100, and don't want to have to calibrate for each new temperature I wish to reach. A few degrees in cooking means the difference between safety and dangerous bacterial growth
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Any thoughts?
Best,
M