An electronic device that automatically records measurements from sensors over time at programmed intervals. Data loggers are essential components of hydrological monitoring networks, recording stage, flow, water quality, and meteorological parameters.
A data logger is a compact electronic device that receives analog or digital signals from one or more environmental sensors, converts them to engineering units, and stores the data in internal memory at programmed intervals. In hydrology and water resources, data loggers are the backbone of automated monitoring networks, recording parameters including water level (stage), flow velocity, precipitation, water temperature, pH, dissolved oxygen, turbidity, conductivity, and meteorological variables. Modern data loggers feature low power consumption (solar or battery operation), large memory capacity, multiple sensor input channels, programmable sampling and recording intervals, and on-board data processing capabilities (averaging, peak detection, event-triggered recording). Communication options include cellular, satellite (GOES, Iridium), radio, and Wi-Fi telemetry, enabling near-real-time data transmission to web-accessible databases. The USGS National Water Information System (NWIS) relies on data loggers at over 13,000 stream gauging stations across the United States to provide continuous streamflow data. Data logger programming must account for sensor response time, measurement frequency appropriate to the parameter's variability, quality assurance checks, and data storage capacity between downloads. Common data logger manufacturers in the water resources field include Campbell Scientific, In-Situ, Onset (HOBO), YSI/Xylem, and Sutron.