[Phys-L] Re: question about instrument

[jsd at AV8N.COM (John Denker)]

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