Abstract. The Niwot Ridge Subalpine Forest AmeriFlux site (US-NR1) has been measuring eddy-covariance ecosystem fluxes of carbon dioxide, heat, and water vapor since 1 November, 1998. Throughout this 17-year period there have been changes to the instrumentation and improvements to the data acquisition system. Here, in Part I of this three-part series of papers, we describe the hardware and software used for data-collection and metadata documentation. We made changes to the data acquisition system that aimed to reduce the system complexity, increase redundancy, and be as independent as possible from any network outages. Changes to facilitate these improvements were: (1) switching to a PC/104-based computer running the NCAR NIDAS software that saves the high-frequency data locally and over the network, and (2) time-tagging individual 10-Hz serial data samples using network time protocol (NTP) coupled to a GPS-based clock providing a network-independent, accurate time-base. Since makings these improvements almost two years ago, the successful capture of high-rate data has been better than 99.98 %. We also provide philosophical concepts that shaped our design of the data system and are applicable to many different types of environmental data collection.
A New High Channel-Count, High Scan-Rate, Data Acquisition System for the NASA Langley Transonic Dynamics Tunnel