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Comparison of the ITS-90 at 933,473 K and 1234,93 K / Report on IMGC measurements for Euromet 820
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Water Triple Point Comparison: Plateau averaging or Peak Value?
No full textWith a certain regularity, national metrology institutes conduct comparisons of water triple-point (WTP) cells. The WTP is the most important fixed point for the International Temperature Scale of 1990 (ITS-90). In such comparisons, it is common
practice to simply average all the single measured temperature points obtained on a
single ice mantle. This practice is quite reasonable whenever the measurements show
no time dependence in the results. Ever since the first Supplementary Information for
the International Temperature Scale of 1990, published by the Bureau International
des Poids et Mesures in Sèvres, it was strongly suggested to wait at least 1 day before taking measurements (now up to 10 days), in order for a newly created ice mantle to stabilize. This stabilization is accompanied by a change in temperature with time. A recent improvement in the sensitivity of resistance measurement enabled the Istituto Nazionale di Ricerca Metrologica to detect more clearly the (possible) change in temperature with time of the WTP on a single ice mantle, as for old borosilicate
cells. A limited investigation was performed where the temperature of two cells was
monitored day-by-day, from the moment of mantle creation, where it was found that
with (old) borosilicate cells it may be counterproductive to wait the usual week before
starting measurements. The results are presented and discussed, and it is suggested to
adapt the standard procedure for comparisons of WTP cells allowing for a different
data treatment with (old) borosilicate cells, because taking the temperature dependence
into account will surely reduce the reported differences between cells
Production of a new Tin Cell at INRIM
No full textOver the years some of the INRIM metal fixed-point cells, ≥20 years old,
have shown a variable deterioration consisting in the leaking of some of the metal
through the walls of the crucible. The variation in the deterioration is assumed to be
connected with the frequency with which the cells have been used. New cells are
therefore being produced at INRiM as substitutes for the older cells. A description
of the new cells and their preparation is given, along with a preliminary comparison
between the new cell and the older cell(s)
Some Curious Results with a Gallium Fixed Point Cell
No full textIn 2009, most of the gallium fixed-point cells in use in different
INRIM laboratories were compared with Italy’s national standard. The comparison
has uncovered problems with one of the commercial devices, realizing a temperature
about 0.7mK too low which initially was even changing linearly with time. An additional
series of measurements was undertaken to find out the reason for this behavior,
but not being allowed to open the cell, only a suspicion on the possible cause has
remained. A way is suggested that might give users an indication of such misbehavior
of their cell. The results underline the importance for those NMIs with only a single
cell, for any fixed point, to undertake regular comparisons with another cell as a check
on its behavior
Construction and investigation of six Pt/Pd thermocouples to be used as secondary standards
No full textDeterminazione degli errori e delle incertezze legati ai ponti di resistenza, in uso presso l’IMGC, con l’uso del Resistance Bridge Calibrator RBC100
No full textComparison of the ITS-90 over the range 83,8058 K to 692,677 K – Report on IMGC measurements for EUROMET Project 552
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