most accurate thermometer

[matt b]

Well I have a aqua controller jr that says 80 a cheap digital that says 76 and and reefkeeper that says 83. So whats the most accurate one i can buy? Or how do I calibrate them?

 

[reefforbrains]

Go to a medical supply and pick up a medical grade one.
Keep an eye on all of them but set them to the benchmark of a medical grade therm and then see who slides off the mark first and act accordingly.