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Instrument Control and Onboard Data Handling
Published in Shen-En Qian, Hyperspectral Satellites and System Design, 2020
The spacecraft bus electrical interfaces are defined by the bus and are nominally as follows: Power is at 28 V DC nominal with separate power feeds to all payload units.Pulse commands are used to switch the PFCU on and off, this in turn controls the on/off switching of the other payload units.A MIL-STD 1553B serial interface is used to send multi-bits commands to the PFCU that control the payload operation. This same interface is used to transfer bus ancillary data to the PFCU.A 1-PPS signal provides a GPS reference pulse used to reference all onboard time to Coordinated Universal Time (UTC). This referencing is implemented in the PFCU.
Advances in Wide Area Monitoring, Protection and Control
Published in Ramesh Bansal, Power System Protection in Smart Grid Environment, 2019
Adeyemi Charles Adewole, Raynitchka Tzoneva
A 1 PPS timing system has a pulse train of positive pulses, with the rising edge of the pulses coinciding with the seconds change in the clock. The pulse widths vary from 5 μs to 0.5 s, and the signal is usually a 5.0 V magnitude driving a 50 ohm load. The IEEE Std 1588-2008 Precision Time Protocol (PTP) [13] is a time synchronization method based on Ethernet communication architecture with a guaranteed accuracy of 100 ns. This profile was adopted for power system applications as specified in the IEEE C37.238-2011 Std. Aside from the GPS, other Global Navigation Satellite Systems (GNSS) time references can be obtained from the Russian-based GLONASS and the European-based Galileo systems. The particular GNSS time reference to use depends on the following: (1) accuracy, (2) coverage area, (3) duration of continuous availability, (4) reliability, (5) integrity, and (6) hold-over capability during loss of satellite synchronization.
Time Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Time measurements can be divided into two general categories: time interval measurements and time synchronization measurements. Time interval measurements determine the duration or elapsed time between two events. Time standards typically produce 1 pulse per second (pps) signals. The period of these signals is a standard second that serves as a time interval reference. Many engineering and scientific applications require the measurement of time intervals much shorter than 1 s, such as milliseconds (ms, 10−3 s), microseconds (μs, 10−6 s), nanoseconds (ns, 10−9 s), picoseconds (ps, 10−12 s), and femtoseconds (fs, 10−15 s). Thus, the instrumentation used to measure time intervals always requires subsecond resolution.
All-optical wavelength reuse with simultaneous upstream data and PPS timing signal transfer for flexible optical access networks
Published in Journal of Modern Optics, 2019
G. M. Isoe, E. K. Rotich, D. K. Boiyo, S. Wassin, A. W. R. Leitch, T. B. Gibbon
In this paper, we propose the use of an erbium-doped fibre amplifier (EDFA) gain saturation with a holding beam to achieve all-optical wavelength reuse with simultaneous upstream data and pulse-per-second (PPS) timing signal transfer of a 8.5 Gbps NRZ signal and 1 PPS timing signal over 24.7 km SMF fibre using a single DFB laser. Our proposed approach is fully optical, comply with strict budget cost and simplified maintenance, integrable with existing optical access networks, and for implementation purposes does not require any customized or additional optics hardware. This technique is novel and is appropriate for flexible optical access networks applications operating at data rates of up to 8.5 Gbps.
Household slow sand filter efficiency with schmutzdecke evaluation by microsensors
Published in Environmental Technology, 2022
Antonio Wagner Lamon, Paulo Marcos Faria Maciel, José Roberto Campos, Juliano José Corbi, Patrick Stuart Morris Dunlop, Pilar Fernandez-Ibañez, John Anthony Byrne, Lyda Patricia Sabogal-Paz
A data acquisition system was developed specially for application in LabView® language. The microsensors were vertically introduced into the non-woven blanket samples by a micro-stepper, also controlled by software. The microsensor position (depth in µm), which appears on the X axis, and the DO concentration at 1 pps (point per second) acquisition speed and 20 µm spatial resolution, visualised on the Y axis, were obtained in the DO microprofiles.