Temperature calibration

I've been running a RKL for a couple years on my DT. Recently bought a 2nd one for my cube and got it set up last week. I've got a 2 degree difference between the two. I've tested both out in my DT (all for combinations of new/old probe and new/old head unit) and part of the variation is between the head unit and part of the variation is with the probe:


Old Head unit New head unit


Old probe 78.3 77.0


New probe 77,8 76.3


I've talked to Digital Aquatics and they have told me how to calibrate the unit. I think the old unit is probably most accurate, but I don't really have a good way to confirm that for myself. Anyone have a good source for checking the accuracy of the thermometer????

 

That would be great if I could borrow it. I will get a hold of you tomorrow. Thanks!