Temp probe calibration

[artguy]

How do you calibrate temp probes from Brewers hardware? I have a fixed 4" probe that is 1.5 degrees off.

[bbrally]

You've probably already entered the thermistor coefficients from the Brewers hardward website in the the BCS, and still found an error in readings.

My probes from BH were also out a couple of degrees of each other, probably due to manufacturing tolerances, and I did the following to bring them inline.

I prepared three water baths for testing of the probes. One ice water stirred well so as to allow the water to reach 0c. One of boiling water for 100c. And one of hot water at about 65c measured with an accurate thermometer.

I placed the probe(s) in the center of each of the baths without letting it touch the sides of the container or other probes and let the temp readings stabilize. (I used a piece of wood with a 1/4" holes drilled in it that I could stick the probes into and then placed the wood on top of the pot of boiling/freezing water.) I then recorded the average resistance values over a dozen or so readings and entered these values into the SH thermistor calculator to produce accurate coefficients.

There is a posting on the forum with links to calculators and calibration techniques: http://forum.embeddedcc.com/viewtopic.php?f=6&t=10

It takes a bit of work, but it's the only way to know that your temps are proper.