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This company, which specializes in environmental control for cultural institutions, was briefly described in the July 1989 issue of this Newsletter, on p. 75.
To insure good environmental conditions for the books and artifacts in our museums, historical societies, libraries and historic buildings, it is essential to monitor the temperature and humidity. Each of the critical zones in the building should be monitored, and the daily minimum and maximum readings recorded. Otherwise it is practically impossible to know whether you are providing the right climate, one that will keep the books and artifacts available for future generations.
A very affordable direct readout precision meter with minimum and maximum memories just came on the market, making it possible for most institutions to monitor all the zones in their buildings: the Thermo Hygro, from Interstate, Inc. This unit is not a datalogger, nor does it carry the price tag of a datalogger. On the other hand, it is more than a minimum-maximum thermometer because it also records the minimum and maximum humidities, and retains these four values in its memory until manually reset. This gives you the same information you look for in a hygrothermograph tracing: the change in temperature and RH over a given period of time. If you need to know the variation in temperature and relative humidity for each day, you will record the readings and reset the meter daily; if you are interested in weekly variations, you only need to visit it weekly.
At many of the facilities I work with, the people would like to have a full-blown computer system monitoring the environment, but don't have the budget for even a single hygrothermograph. This unit is inexpensive enough to begin a program. It sells for under $75 through a refrigeration house I deal with; a few weeks ago the lowest price on an instrument with the same specifications was $450. I have conducted several tests on the cheaper model, and found it to be accurate, within 2 degrees F and 5% RH. It is precalibrated and no recalibration is necessary. The battery has to be changed once a year.
I have managed to contact the importer of this device, who said he would make this unit available to the readers of this article for $59 for a limited time. If you are interested, call me for details.
Entering the results in one of the Big Three spreadsheets will allow you to analyze the data graphically. If this sounds too technical, just take your results to the local high school and see the computer instructor. Ask him if he would be interested in having his students process the data in a spreadsheet, analyze it in every way possible, and then prepare reports, including graphs and charts. The instructor will love you for providing him with real world projects, and the students will get an opportunity to be part of your organization.
Once the data is in a form that you can understand, problems with the HVAC, if any, will become immediately apparent. The more consistent the recordings of the temperatures and humidities, the more accurate your analysis can be.