For the Millennium we have automated most of the Slim Fixed Point Cells apparatus so that untrained personnel can have the ITS-90 values available all day, each and every day. An article from Isotech explains this philosophy in detail, please ask for a copy.

The Cells themselves are made from the highest quality graphite and quartz glass and are sealed with 1 atmosphere of 6N (99.9999%) pure argon at the freeze temperature. The metals are also 6N purity to ensure the most accurate realisation of ITS-90.

Isotech’s Slim Fixed Point Cells can be used to calibrate temperature sensors, either as the metal within them melts, or as it freezes.
Typically, says CCT/96-8, a 6N pure cell will melt over 80% of its plateau within ±1mK. Exceptionally Isotech’s Gallium Cell will melt over ±0.2mK.

The purpose of Slim Cells is to calibrate shorter sensors, and so large apparatus is inappropriate. A Secondary Laboratory needs easy-to-use, economically priced apparatus which needs to be smaller and bench mounted.