Greetings:
I have used several different types of Dataloggers and have found that
the HOBO loggers are the most cost-effective and easy to use for the
$$$. I also like their software. It is easily exportable to Excel and
the data can be manipulated for analytical purposes. The customer
support that I have received from Onset has been outstanding.
As I am familiar with your site, I would recommend purchasing HOBO Pro-8
loggers because they will provide data over the entire range of RH 0 -
100%. The standard Hobo 8, will flat-line around 25%, the bottom of its
range. You will also need to purchase one HOBO Pro-8 for installation
outside so that you can compare building performance against ambient
conditions. You may need to purchase a rain guard and/or solar shield
(also available from Onset) depending upon where you locate the exterior
logger because they need to be protected against rain and direct sun.
I would recommend purchasing a Shuttle from Onset if you are going with
the HOBOs because you can take it from logger to logger and download
each before taking the Shuttle to the computer for downloading. The
Shuttle will relaunch the logger using the settings that were
established when the loggers were first deployed.
Identification of interior locations can be tricky, my general advice is
to look carefully at the structures and the systems that are installed
there to determine if there are different zones, and then place your
loggers accordingly so that they will record the conditions in each zone
where you have critical collections or where you may desire to place
collections that are T and RH sensitive. For comparative purposes, make
sure that the loggers are set and deployed on the same schedule. The
Hobos are good for this because they have a delayed launch capability.
If your finances do not permit placing a logger in each zone, consider
doing the most critical zones the first year, and relocate the loggers
to other areas the following year.
Be sure to place the loggers where they will not be in direct sunlight,
close to heating or cooling equipment especially forced air or directly
above radiators, or any other type of heat or moisture generating
equipment. As with hygrothermographs, loggers should be placed in the
"object zone" to monitor the air that will be around an object.
When the loggers first arrive, they should be bench-checked to determine
if they are in calibration with each other and working properly. This
is done through deploying all of the loggers in the same location for
the same period of time with the same frequency of sampling. The data
can then be downloaded to the computer and the logger data compared
against each other. Any loggers that are "way out" of calibration or
not working properly should then be returned to the manufacturer. The
calibration should be bench checked every year as well to ensure that it
is still operating within acceptable margin of errors. The Hobo Pro-8s
also contain a small packet of silica gel that should be checked
annually to determine if it needs regeneration. I received the following
communication from Onset: When the desiccant package turns pink it
should be disposed of (WCJ Edit: actually replaced) or placed in an oven
at about 140 degrees for 15 minutes. Onset sells 25 replacement packets
of silica gel for $6.00.
As for frequency of sampling, it is important to set sampling rate so
that you get enough data to observe conditions of concern, but not too
much. I currently have several monitoring projects in progress where
the loggers are set to sample every 30 minutes and are downloaded once a
month. This provides me with good trendline data for evaluation of
indoor conditions in gallery spaces such as the Museum or in domestic
settings like SB house or an historic house museum.
I recommend that each location be monitored for a year in order to get
an understanding of how the conditions may change over the course of the
seasons.
I have attempted to provide a general overview to monitoring and
establishing a program based on what has worked for me on a number of
projects. I haven't even touched on techniques for evaluating
monitoring data. Please remember that each monitoring project needs to
be based upon the circumstances of the site and the objectives for
monitoring. I am sure that there are factors that I may have glossed
over or omitted which our conservation colleagues on this list may feel
need to be added.
There are numerous good references on environmental control and
monitoring. Check out Conservation On-Line
(http://palimpsest.stanford.edu/)
I hope that this has been helpful
Wendy Claire Jessup
President and Conservator
Wendy Jessup and Associates, Inc.
1814 N. Stafford St,
Arlington, VA 22207
(703) 522-2801
FAX: (703) 522-2802
[log in to unmask]
-----Original Message-----
From: Museum discussion list [mailto:[log in to unmask]] On
Behalf Of Christian Carr
Sent: Monday, May 03, 2004 6:53 PM
Subject: Dataloggers?
Hello all--I am in the happy position of having some funds in hand that
need to
be spent this fiscal year, and am considering purchasing dataloggers. I
would
use these for teaching environmental monitoring in our museum studies
classes
while monitoring the spaces and storerooms in the Sweet Briar Museum and
in
Sweet Briar House, our National Register property that serves as the
college
president's home and where the bulk of our decorative arts collection is
on
display. I am especially interested in the latter as a geothermal
system was
just installed and I am concerned with monitoring conditions there to
insure
that the collections are not adversely affected by this new system.
My experience with environmental monitoring has been limited to
hygrothermographs, but I have heard that dataloggers can either transfer
readings directly to a computer, or can easily be inserted into a USB
port to
download readings. I am sure that you list members will be able to give
me good
advice regarding sources for these dataloggers, how many I would need (1
per
room? one on each side of a large room? 1 for each case?), what the
approximate costs might be, and how to set up a program of retrieving
and
recording the information.
Many thanks in advance for any assistance you can provide. You may
contact me
off-list at [log in to unmask] if you prefer--I will be grateful for any and
all
words of wisdom!
All best,
Christian
Christian Carr
Acting Director, Sweet Briar Museum
Assistant Professor, Arts Management
Sweet Briar College
Sweet Briar, VA 24595
434.381.6246-phone
434.381.6132-fax
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