The U.S. Army Corps of Engineers (USACE), CHL, FRF, had a need for a remote real-time data collection system to control instruments and log and communicate data from five observing stations in the Currituck Sound Estuary, NC1. These stations, referred to as the Currituck Sound Array (CSA), collect a suite of meteorological and oceano-graphic data including wind, air temperature, humidity, incoming solar radiation (above and below water), waves, currents, water level, salinity, and water temperature, as well as turbidity and many other water quality parameters. This array of instruments has a variety of control commands, sample routines, and output data formats. Additionally, the CSA was designed to act as a natural laboratory for estuarine research and as an instrument and model test bed. These capabilities required a reliable and flexible system that would allow easy modification of sampling schemes, the ability to log as many as 15 instruments with a single logger, and allow the incorporation of additional and novel instrumentation with minimal effort and expense.

Custom built data logger and its components

The custom loggers were built upon single board computers (SBC) running the Linux operating system. They effectively have the same functionality as a personal computer, overcoming many of the limitations of off-the-shelf loggers. Additionally, off-the-shelf loggers typically operate on a very limited set of commands. These custom Linux-based loggers have a much more diverse and powerful selection of commands, overcoming many of the unique challenges of real-time data collection with robust code and programmatic “watchdogs” that can automatically make sure the logger, instruments, and communications are operating as intended.

The “brains” of the data loggers are Technologic Systems TS-7250-V2 SBCs. While there are many suitable SBCs on the market, these particular units were chosen based on size, cost, processing power, number of available analog and serial ports, ruggedness, and operating temperature range.

Remote data logging units are typically deployed at exposed locations and housed in small weather-proof enclosures requiring them to be compact, energy efficient, and able to operate at temperature extremes. The TS-7250-V2 is designed for industrial applications making it rugged and reliable. They are compact (10 cm × 11 cm) and operate over a large temperature range (-40°C to 85°C). They are energy efficient, drawing approximately 200 milliamps (mA) at 12 volts (V).

Most meteorologic and oceano-graphic instruments output an analog data signal or communicate via serial communication protocols (e.g., RS232 or RS485). The TS-7250-V2 comes equipped with five channels of analog-to-digital conversion (ADC) and three serial ports. Additionally, up to three PC104 peripheral boards can be added to expand the ADC or serial communication capabilities. Each additional board can add 12 or more ADC channels or four serial ports. In the present configuration of this data logger, three TSER4 serial communication boards (also from Technologic Systems) have been added to expand the logging capabilities to a total of five ADC channels and 14 serial communication ports. One serial port is reserved for direct communications with the unit. In this configuration, all serial communications are RS232.

This work was done by Patrick J. Dickhudt and Kent K. Hathaway for the Army Corps of Engineers. ERDC-0003

This Brief includes a Technical Support Package (TSP).
A Custom Data Logger for Real-Time Remote Field Data Collections

(reference ERDC-0003) is currently available for download from the TSP library.

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