The Omega TRCIII-A Ice Point Reference relies on the equilibrium of ice and distilled, deionized water at atmospheric pressure to maintain six reference wells at precisely 0C. Each well extends into a sealed cylindrical chamber containing the distilled deionized water. The outer walls of the chamber are cooled by thermoelectric cooling elements.

The alternate freezing and thawing of the ice accurately maintains a 0C environment around the reference wells. The TRCIII-A has a built in temperature readout [C/F] with 0.1 resolution.