GOSA (The Geyser Observation and Study Association) Geyser
Data Logger

Data Logger Background

Some Analysis

by Ralph Taylor
Reprinted from The Geyser Gazer Sput, a bimonthly publication of GOSA.
As many of you may know, I have had a research permit for the past four years to monitor geyser activity using electronic data loggers. For those years I also assisted Tim Thompson, the Geothermal Technician, by downloading and redeploying the National Park Service data loggers late in the season after Tim left the Park. This summer one of my jobs as an NPS volunteer for Nancy Hinman was the deployment and management of the NPS data loggers in addition to my own loggers. At the start of the summer we had l6 loggers between my loggers and the NPS loggers. Over the Course of this summer we acquired several more; the total is now 29 loggers, 25 of which are currently in use (the other four just arrived).

Perhaps a little introduction to data logger terminology is in order. A data logger, Figure 1, is a device that records some kind of information (in our case, temperature) at user-specified intervals. The logger itself uses a single chip microcomputer and a memory chip to record the data as required. The sensor for the loggers we use is a thermistor, an electrical resistor with the property that the resistance to electrical current varies with temperature. The logger measures the temperature by measuring the resistance of the thermistor and uses a calibration chart or equation to determine the actual temperature. The logger is deployed by placing the thermistor in a location where the runoff water from an eruption or overflow passes over the sensor. The logger itself is located in a sheltered location nearby. The NPS requires that data loggers on front country features be placed out of sight, so we typically bury the logger in sinter sand, cover it with