[time-nuts] Temperature sensor

[Mark Sims]

You don't want to do freezing point tests with gallium...  it really likes to supercool without freezing.  A gallium triple point cell is the way to go.   Good reading here: http://www.nist.gov/calibrations/upload/met15-79.pdf
I once built some precision temperature measurement equipment that we calibrated against an ice bath (using purified,  degassed,  DD water) and boiling water (pressure corrected).  The devices were then sent off to one of the national labs where they did calibrations against water and gallium triple points (and who knows what else).  Our cheapo calibrations agreed  in the millidegree area.  Their final calibration polynomial was something like a 23rd order poly...