[Phys-L] Re: question about instrument

[anngeorg at PACBELL.NET (Bernard Cleyet)]

"Chilled mirror hygrometers have been widely used in laboratories and
industry since the early 1960s. Their advantages include the fundamental
measurement principle, high accuracy, and traceability to national
standards. Their shortcomings have until recently been a sensitivity to
contaminants that requires frequent maintenance, a slow response at very
low frost points, and a near inability to achieve measurements below 1
ppm."  [JD's first reference]



At least as early as 1877 when Alluard invented one using a volatile
[e.g. ethyl ether] to cool a mirror.  I used a crude one (Cenco?) during
the intro, lab at UCSB, 1955.


bc, who has(d) a commercial discarded one intended to measure the dew
point of bottled gas (3K PSI)

John Denker wrote:
> James Mackey wrote:
>
> > Perhaps someone can help with this question.  Does anybody know
> > anything about a humidity device named "Protimeter PLC digital
> > hygrometer"? Or if anyone knows a website with info.  I can find the
> > mfg site, but no info on this device.
>
>
> There are two main kinds of hygrometers
>   -- chilled mirror, direct measure of dew point
>      (good for humidity in air)
>   -- RF, exploiting the huge polarizability of the water molecule
>      (good for moisture in solids e.g. grain or lumber)
>
>    http://www.google.com/search?q=protimeter+principle
> which leads immediately to
>    http://www.sensorsmag.com/articles/0700/46/main.shtml
> among others