And as you realise "inexpensive but accurate at 0.05C = impossible"

On 12/24/08, Vasile Surducan <piclist9@gmail.com> wrote:
> On 12/24/08, Alan B. Pearce <Alan.B.Pearce@stfc.ac.uk> wrote:
> > >0.05C? 0.5 is hard already. 0.05/40, that means 0.1% accuracy in T!
> > >
> > >What to calibrate? 3 phase water in 1 atm? to hard.
> >
> > No, boiling point of water is inaccurate, as it is too hard to hold the
> > pressure accurately.
>
>
> No, the steam pressure is constant. He need a boiling water device
> with steam collector near ambiant pressure (manufactured for
> thermometer calibration) and at least four calibrated thermometers
> with better precision than 0.05C.
> In my town, the boiling temperature of bidistilated water is between
> 99.2 C and 99.8C depending on weather.
>
> I've made only one 0.05C accuracy thermometer. Resolution of the A2D
> is the last problem, there are 100 others. The most difficult one is
> to get calibrated thermometers. And to understand the effect of sensor
> mounting into the probe.
>
> Vasile
>
>
>  AFAIK all high accuracy accuracy standards use solid to
> > liquid phase of various substances.
> >
> > So to achieve calibration in the OPs range, my suggestion is ice at 0C, and
> > gallium at 38.5C (check this one, I am going from memory). There may well be
> > others nearer the outer ends of the range he wants to measure.
> >
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