Mini Metal-Cased Fixed-Point Cells

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Mini Metal-Cased Fixed-Point Cells (287.24 KB)

Mini metal-cased fixed-point cells have been developed for the triple point of water (TPW), the melting point of gallium (MPG), and the freezing point of indium (FPI). The outer case is made from stainless steel. An inner vessel, used for the MPG and FPI, is made of virgin PTFE. The design of the new cells is described in detail.

Realization methods were investigated for each of these newly designed fixed-point cells. Data was obtained from melting and freezing the cells. These cells were compared with traditional fixed-point cells. The differences between the new small cells and traditional size cells were well within 3 mK for the MPG and the FPI. The differences of the newly manufactured TPW cell and a traditional TPW cell were within 0.5 mK, but this difference was found to increase with time. This degradation is addressed.

The stainless steel–cased cells are much less fragile than Pyrex and quartz glass, so the new cell design fits many applications where more durability is desirable such as in ocean vessels or mobile labs, where traditional fixed-point cells are easily broken or damaged.