Many different makes of hygrothermographs are available, from
many different places. Without endorsement, there are for
instance the giant scientific supply houses, such as
Cole-Parmer, and Fisher Scientific. I used to favor clock-drive
recording hygrometers. I did so because of my faith in "Occam's
Razor," i.e., "Exchew complexity" (put differently, "KISS").
Such instruments are as technologically complex as a grain
shovel. The drive mechanism is the result of continuous
development over half a millenium. The sensing units are on the
one hand a simple bimetallic strip, and a bundle of
hygroscopically-reactive hair. Movement in both is translated
and amplified through simple mechanical linkages, to pens
tracking analog data onto paper charts. It is all eminently
understandable, adjustable, calibratable, and repairable on the spot,
by anyone "of the meanest capacity" . . . all, that is, except
the clockwork drive. And there is the Achilles' heel.
Clock repair - of mechanical clocks -is not exactly a rising
employment field. Repair is hard to find locally. Most if not
all vendors maintain repair services, but this means shipping
both ways, and waiting.
That is why I am being moved reluctantly in the direction of
data loggers. I have no panegyric for them, but they are
generally speaking competitive in price with hygrothermographs.
I am particularly interested in the PEM being developed by the
Image Permanence Institute at RPI.
According to ERIN E. GAMSE:
>
> I am trying to purchase a recording hygrothermograph for monitoring
> in a newly restored 1904  building.  Does anyone have any strong
> recommendations for brands and/or suppliers.  Is Belfort in Baltimore
> still in favor?  Any tips or things to watch out for?
>