Does waterproofing Thermochron iButton dataloggers influence temperature readings?

Abstract

Miniature Thermochron iButton dataloggers have transformed the ways in which researchers collect thermal data. However, one important limitation is that these dataloggers are not waterproof, which can lead to device failure and loss of data under field conditions. Several methods have been used to increase their water resistance, but no study to date has investigated whether any of these techniques affects the accuracy of temperature readings. Waterproofing potentially could affect the accuracy of iButtons by biasing temperatures or altering rates of warming and cooling. We compared temperature profiles of unmodified Thermochron iButtons (model DS1921G) to iButtons that we coated with a clear plastic dip (designed to coat tool handles) to determine whether this waterproof coating affects the accuracy of temperatures they record. We also compared temperatures recorded by uncoated and coated iButtons that were embedded within physical models that mimic frog body temperatures. Finally, we used our field data to test whether coating iButtons with plastic prevents failure of dataloggers during fieldwork. Although we found statistically significant differences between the temperatures recorded by uncoated and coated iButtons, and also between uncoated and coated iButtons embedded in frog models, these effects were relatively small (0–1.3 °C). We also found that coating iButtons with plastic reduced the likelihood of device failure under field conditions (from 8.3% to 0%). We conclude that coating Thermochron iButtons with plastic is an affordable and reliable method of waterproofing dataloggers that prevents device failure and data loss with minimal influence on temperature readings.