I wrote earlier that the bias "offset" adjustment knob on the Omega HH12B thermocouple only adjusts to a fraction of one degree. That's wrong. I remembered that wrong. Or I hesitated to turn the screw the whole way. Anyway, just now I set it to the T1-T2 mode, and then turned the OFFSET all the way for T1. It goes from +4.3 to -4.8 deg C. In other words, it goes up or down about 4 degrees.
So obviously, a 5 deg C bias in one of these instruments is not unheard of. In fact, right now I am trying to turn the knob back to zero to make it go away (to make T1-T2=0) and I find it is a little tricky. You have to put both probes into water I think, and turn slowly. I cannot easily bring it down below 0.3 deg C, in air. Perhaps someone was impatient and did not want to bother evening out the bias, after adjusting the OFFSET screws. On a completely unrelated subject, you might want to see this video of a wild turkey chasing a television producer: http://www.cnn.com/video/#/video/us/2011/10/07/turkey-attacks-producer.kxtv - Jed
