PC-Based PCM Telemetry Data Reduction System Hardware

The Solar Energy Research Institute's (SERI) Wind Research Program is using pulse code modulation (PCM) telemetry systems to study horizontal-axis wind turbines. SERI has developed a low-cost PC-based PCM data acquisition system to facilitate quick PCM data analysis in the field. The SERI PC-PCM system consists of AT compatible hardware boards for decoding and combining PCM data streams and DOSsoftware for control and management of data acquisition. Up to four boards can be installed in a single PC, providing the capability to combine data from four PCM streams direct to disk or memory. This paper describes the SERI PC-PCM system hardware, focusing on the practicality of PC-based PCM data reduction. A related paper highlights our comprehensive PCM data management software programwhich can be used in conjunction with this hardware to provide full 'quick-look' data processing and display. The PC-PCM hardware boards support a subset of the Inter-Range Instrumentation Group (IRIG) PCM standard, designed to synchronize and decommutate NRZ or Bi-Phase L PCM streams in the range of 1 to 800 Kbitsfsec at 8 to 12 bits per word and 2 to 64 words per frame. Multiple PCM streams(at various rates) can be combined and interleaved into a contiguous digital time series. Maximum data throughput depends on characteristics of the PC hardware, such as CPU rate and disk access speed.