Instruments

Every USCRN observing station is equipped with a standard set of sensors, a data logger, and a satellite communications transmitter. Some of the measured parameters (e.g. temperature, precipitation, and soil conditions) have multiple sensors for redundancy and independent validation. Off-the-shelf commercial equipment and sensors are selected based on performance, durability, and cost.

USCRN's climate-related variables and associated sensors currently include:

Air Temperature	Three platinum resistance thermometers housed in fan aspirated solar radiation shields
Precipitation	An inlet-heated, wind-shielded weighing rain gauge (configured with three load cell sensors), precipitation (wetness) detector, and an auxiliary tipping bucket gauge.
Wind Speed	A 3-cup anemometer at the same height as the air temperature shield intakes.
Solar Radiation	A silicon pyranometer
Surface (Skin) Temperature	A precision infrared temperature sensor pointed at the ground surface
Relative Humidity	A capacitive thin-film polymer humidity sensor providing accurate and stable measurement even in environments with high humidity
Soil Temperature & Moisture	Moisture sensors with built-in thermistors installed at specific depths: 5, 10 20, 50 and 100 cm.

Temperature sensors are placed on a typical 3 meter (10 ft.) instrument tower at 1.5 meters above the ground surface. Locations which experience high snowfall and snow depth are given special consideration. The instrument system is designed to accommodate additional sensors on the tower without disrupting the physical site.

Hourly and sub-hourly values are stored in a data logger attached to the tower. A geostationary satellite transmitter sends the data to the National Centers for Environmental Information where the data undergo a quality control check and are placed on the Web continuously as the data arrive.

Highly accurate measurements and reliable reporting are critical. Instruments are calibrated or verified annually, and maintenance includes routine replacement of aging sensors. The performance of each station's measurements is monitored on a daily basis and problems are addressed as quickly as possible, typically within days.

Stations are powered by a 12-volt battery bank sized by location with a charging method designed to run the station for several days. The battery system is charged using a combination of AC, solar, and/or methanol fuel cells (mainly in AK).

Available equipment and instrument documentation is available below. Please contact the USCRN Science/Technical Contact for additional information.