Netmeter software reads a data stream from up to 250 networked phasemeters, synchronizes the data, saves the reduced data to disk (after applying a low-pass filter), and provides a Web server interface for remote control. Unlike older phasemeter software that requires a special, real-time operating system, this program can run on any general-purpose computer. It needs about five percent of the CPU (central processing unit) to process 20 channels because it adds built-in data logging and network-based GUIs (graphical user interfaces) that are implemented in Scalable Vector Graphics (SVG).
Netmeter runs on Linux and Windows. It displays the instantaneous displacements measured by several phasemeters at a user-selectable rate, up to 1 kHz. The program monitors the measure and reference channel frequencies. For ease of use, levels of status in Netmeter are color coded: green for normal operation, yellow for network errors, and red for optical misalignment problems. Netmeter includes user-selectable filters up to 4 k samples, and user-selectable averaging windows (after filtering). Before filtering, the program saves raw data to disk using a burst-write technique.
This work was done by Shanti Rao of Caltech for NASA's Jet Propulsion Laboratory.
This software is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (626) 395-2322. Refer to NPO-45505.
This Brief includes a Technical Support Package (TSP).
Multichannel Networked Phasemeter Readout and Analysis
(reference NPO-45505) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the Multichannel Networked Phasemeter Readout and Analysis, referenced as NPO-45505 in NASA Tech Briefs. It serves to disseminate information about aerospace-related technological advancements that may have broader scientific, commercial, or technological applications.
The core of the document focuses on the operation of a beam launcher system used for optical metrology. This system features two outputs: the reference and the unknown. The reference measures the distance between beam launchers and near corner cubes, while the unknown measures the distance to far corner cubes. By continuously monitoring the phase difference between these two signals, the system can accurately measure the displacement of the corner cubes relative to each other.
The primary light source for this metrology system is a diode laser stabilized to the saturated absorption line of acetylene, operating at approximately 194.37 THz. The laser output is amplified and split into two acousto-optic modulators, which differ in frequency by 300 kHz. The modulated signals are then distributed to beam launchers via blue polarization-maintaining fibers, designed to minimize the effects of mechanical vibrations.
The beam launchers project light onto corner cubes, and the returned light is mixed to produce the reference and unknown optical signals. These signals are intensity modulated at 300 kHz and processed through a series of wavelength division multiplexing (WDM) filters before being sent to zero-crossing detectors. These detectors convert the optical intensity into TTL signals, which are then processed by phasemeters implemented in FPGAs. The phasemeters measure the phase difference and transmit the data as UDP packets to a host computer.
The document also includes operational instructions for setting up and shutting down the laser and associated equipment, emphasizing the importance of maintaining the laser's temperature and ensuring proper power management.
Overall, this Technical Support Package provides a comprehensive overview of the optical metrology system's design, operation, and potential applications, highlighting its significance in precision measurement and monitoring in various fields, including aerospace and engineering. It also outlines the procedures for using the system effectively, ensuring reliable and accurate data collection.
