Hygrothermographs

I have used the Qualimetrics Hi-Q model #5020-A for ten years with
no major problems.  When calibrated, the instrument has never been
off more than 1 or 2 degrees in temperature or 1 or 2 percent in rH.
My calibration schedule is admittedly very irregular - usually
several months to a year between calibrations - but the instrument
has been consistent in its measurements.

When conditions are dry (like in winter), the recording pens make a
very faint line; in high humidity conditions, the ink line is vivid
again.  I have changed the recording pens only once in ten years,
when they really dried out.

The instrument runs on two AA batteries and seems to take a year or
two to use them up.

I like the fact that the hygrothermograph is adjustable for
recording conditions on a daily, weekly, or monthly basis.  The
charts are a bit expensive (when I ordered them earlier this year,
they were $25 for a pack of 55 weekly charts, $125 for a pack of 400
daily charts). I always calibrate the instrument when changing to a
new pack of charts. Each pack is trimmed a little differently; the
pen lines may not be at the same height as on a chart from a
previous pack.

The supplier I have used - Scientific Sales, Inc. (P.O. Box 6725,
Lawrenceville, NJ, 08648) - has always been timely in fulfilling
orders and helpful in explaining their products.

Bonnie Parr
Historical Documents Conservator
Illinois State Historical Library

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                  Conservation DistList Instance 12:9
                  Distributed: Thursday, July 9, 1998
                        Message Id: cdl-12-9-008
                                  ***