Climate Notes is a free e-newsletter published by the Image Permanence Institute and designed for collection care staff in cultural institutions. Climate Notes covers a wide range of topics related to managing the environment for preservation.
Over the years, we have often received questions about discrepancies in data logger readings. "Why do my data loggers not agree? Which device is correct?" The short answer is, measuring temperature and humidity is complicated and, even under ideal conditions, two devices will rarely agree. The longer answer requires a more detailed explanation. This issue of Climate Notes will address some of the questions that will guide anyone confronted with different temperature or humidity readings.
Anyone involved in managing the environmental conditions of a library, archive or museum has certainly encountered this dilemma: "These two monitoring devices are not showing me the same values. Which device is right!?" Discrepancies in temperature and relative humidity readings can lead to frustration, especially when the values represent a pivotal point where action may be necessary. These frustrations arise more often over measurements of relative humidity than temperature. In general, temperature is easier to measure and the sensors are more standardized. Humidity measurements are more complex, with myriad parameters that influence the sensors, the standards and methods for calibration, and the reliability of the readings. But, when discrepancies in readings occur, the right questions can help you to move beyond a "he said, she said" dispute.
In fact, careful consideration of each device might prove that each reading was "correct;" or, further investigation could point to why one device might be reading out of range. If you find yourself in this situation...
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When creating our own temperature and relative humidity data logger, the PEM2, our priorities were ease of use, accuracy and long-term stability. The design of the PEM2 was informed by our fifteen years of experience with environmental monitoring in libraries, archives and museums.
Technology and Accuracy
The technology and the calibration of the PEM2 make it a highly accurate monitoring device. The PEM2 measures temperature with a digital sensor that demonstrates consistent linearity across our specified operating range and we guarantee its accuracy to ± 0.5oC. The PEM2 measures relative humidity with a thin-film polymer capacitance sensor and we guarantee accuracy within ±2% RH in the 10%-90% RH range and ±3.5% RH at extremities. These technologies surpass the requirements for recommended environmental monitoring conditions in storage and display areas.
NIST- Traceable Calibration Source
We can guarantee the PEM2's measurements because we individually calibrate each PEM2, checking the performance of the temperature and humidity sensors...
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The Division of Preservation and Access at the National Endowment for the Humanities has announced Sustaining Cultural Heritage Collections, a new preventive conservation grant program. Funds are available for both Planning and Evaluation Projects and Implementation Projects.
Applications must be received by December 8, 2009.
Institutions applying for Planning and Evaluation projects should consider some of the consulting services available from IPI. These grants (which award up to $40,000) are designed to help institutions assess risks to collections and identify realistic approaches for mitigating them. Your institution may want to...
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