• Design Considerations for Networked Data Acquisition Systems

      Cranley, Nikki; Corry, Diarmuid; ACRA Control Inc. (International Foundation for Telemetering, 2009-10)
      Ethernet technology offers numerous benefits for networked Flight Test Instrumentation (FTI) systems such as increased data rates, flexibility, scalability and most importantly interoperability owing to the inherent interface, protocol and technological standardization. However, the best effort nature of Ethernet is in sharp contrast to the intrinsic determinism of tradition FTI systems. The challenge for network designers is to optimize the configuration of the Ethernet network to meet the data processing demands in terms of reliability and latency. This paper discusses the necessary planning and design phases to investigate, analyze, fine-tune and optimize the networks performance.
    • Measuring and Evaluating Best Source Selection

      Corry, Diarmuid; ACRA Control Inc. (International Foundation for Telemetering, 2009-10)
      To properly evaluate and characterize the performance of a bit synchronizer we need to apply a known data stream and then adjust several interference parameters to measure the effect on synchronization performance: white noise, offset and gain variations and frequency and phase shifts. The task becomes more complex when we consider the performance of a best source selector (BSS) which combines the performance of two or more bit synchronizers to achieve better bit error rates and more consistent synchronization than can be achieved with one alone. Each of the parameters (noise, offset, gain, phase) are often different for each bit synchronizer, and may vary over time. In addition the incoming bit streams can drift in time (possibly 100s of bits) with respect to each other. This paper discusses how these parameters are measured, and looks in particular at the problem of evaluating a BSS. Results showing the performance that can be achieved when aligning and combining multiple streams are presented and discussed.
    • Networked Flight Test Instrumentation Data Recording Solutions

      Cranley, Nikki; Corry, Diarmuid; ACRA Control, Inc. (International Foundation for Telemetering, 2009-10)
      An integral component of networked Flight Test Instrumentation (FTI) and Health and Usage Monitoring Systems (HUMS) is the networked Data Recorder. The high data rates achievable in networked data acquisition systems put increased demands on the recorder to support ever faster read and write rates. Key to the success of the networked recorder is the format in which the data is recorded. The data recording file format should be network-centric with a low processing overhead to support the recording demands. In this paper the popular file formats, Chapter 10 and the Packet CAPture (PCAP), that are used for recording networked FTI are analyzed and compared.