Relative Humidity/Temperature Meter

Geoffrey Brown's thoughtful response to Susan Hughes' query is closely
related to one of my current projects.

Over the past three years Roger Marin and I have been working in our
spare time to develop an accurate but inexpensive solid state data
logger.  The major area of concern was the selection of an appropriate
RH sensor.  The one which we have selected is a capacitive sensor
produced by Panametrics, called the MiniCap 2.  It's advantages, to us,
were stability (+/- 2% over 24 months), hysteresis (+/- 1% when ranged
from 10% to 90% and back to 10%), with an operating temperature range of
-40 to 180 degrees Centigrade, and it is unaffected by water condensate.

Although the literature states that this sensor is "...immune to most
reagent vapors...", it will be affected by highly polluted environments.

In this event, the replacement cost of the sensor might be an
inexpensive prod to testing for contaminants in storage or display
areas.

This logger will also log lux hours, an important consideration when
particularly light sensitive artifacts are on display.

People who will be in Nashville for the AIC conference next month can
examine the logger at the Conservation Materials exhibit.

Jack C. Thompson
Thompson Conservation Lab

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                  Conservation DistList Instance 7:75
                  Distributed: Monday, April 18, 1994
                        Message Id: cdl-7-75-001
                                  ***