Test & Measurement

Optical Measurement of Temperatures in Muscles and Tendons

Small, electrically and chemically neutral sensors would be implanted surgically. Miniature fiber-optic-coupled sensors based on optically excited, self-resonant microbeams have been proposed for measuring temperatures within muscle fascicles and tendons. The proposed sensors could be used in medical and biological research on humans and other animals. The proposed sensors would be variants of those described in several previous articles in NASA Tech Briefs: "Proximity Measurement of Pressure and Temperature" (NPO-20223), Vol. 22, No. 1 (January 1998), page 48; and "Measurement of Stresses and Strains in Muscles and Tendons" elsewhere in this issue.

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Measurement of Stresses and Strains in Muscles and Tendons

Small, electrically and chemically neutral sensors would be implanted surgically. Miniature fiber-optic-coupled sensors based on optically excited, self-resonant microbeams are being developed for measuring stresses and strains within muscle fascicles and tendons. These sensors could be used in medical and biological research on humans and other animals, or to obtain data for the design of lifelike robots.

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Broad-Band, Noninvasive Radio-Frequency Current Probe

This circuit responds in approximately constant proportion to current over a wide frequency range. An instrument that noninvasively measures alternating current over a broad frequency band (typically from about 0.3 to about 110 MHz) has been invented. This instrument could be especially useful for assessing radio-frequency hazards by measuring currents in various parts of humans or personnel exposed to radio-frequency electromagnetic fields.

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Web-Based Technology Distributes Lean Models

Users can share models while protecting intellectual property. Everybody creates models. These models are used to understand how products will hold up to the stresses, use, and abuse of real-world deployment; analyze the impact of design decisions on cost; simulate interactions; or evaluate numerous other metrics. Unfortunately, because of the variety of software tools available and the cost of acquiring them, models may not be compatible with the software used by customers and suppliers. Sharing models creates the fear of exposing intellectual property, especially if those sharing the models can understand the source code.

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Improvements in a Lightning-Measuring Instrument

Some improvements have been made in the instrument described in "Instrument Records Magnetic Fields Generated by Lightning" (KSC-11769) NASA Tech Briefs, Vol. 19, No. 4 (April 1995), page 38. To conserve battery energy, the instrument was made to record the output of only one of three mutually orthogonal loop antennas and to operate in a "sleep" mode except when "awakened" by a lightning strike. Unfortunately, with this energy-conserving strategy, sometimes even a nearby lightning strike could fail to wake the system up on time to record the first strike. The improvements, directed toward overcoming this trigger deficiency, include (1) replacing the "sleep" mode with a mode in which the signals from all three antennas are sampled sequentially at a reduced rate and multiplexed onto one channel and (2) modifying the triggering scheme and the "awake" mode so that once a signal in at least one channel exceeds the trigger threshold, the signals from all three antennas are sampled at a high rate simultaneously on three digitizing channels for 100 µs. Signal samples acquired at the reduced rate for the past 100 µs at the moment of triggering are stored, along with the samples acquired at the full rate for the 100 µs following the moment of triggering.

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A Lightweight Ambulatory Physiological Monitoring System

Readings of multiple sensors are recorded for subsequent playback and analysis. The Autogenic-Feedback System-2 (AFS-2) is a biomedical instrumentation package that was designed and built at Ames Research Center for use during the September 1992 Spacelab-J (STS-47) mission. The AFS-2 performed successfully during that mission and was rated by members of NASA's Astronaut Office as the best instrument of its kind because of its high data quality, ease of operation, and minimal time for setup and operation. Because of its small size, this system offers comfort and mobility greater than those of other systems developed for the same purpose.

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Program for Controlling Digital Instrumentation Recorders

A computer program enables the simultaneous monitoring and control of two commercial digital instrumentation recorders, each comprising a variable-rate buffer and a data tape recorder. The program can issue all standard tape-motion-related commands (fast forward, rewind, record, forward, reverse, and eject) plus commands for tape search, time code, and buffer settings. The program provides a graphical user interface that facilitates control by the user and displays the operational statuses of the buffers and tape recorders. The program generates a log file that includes a time and date stamp for each control command sent to, and response received from, each buffer and recorder. An option exists in the program to produce tape copies by dubbing from one recorder to the other. The program can also be used to effect a procedure in which data are recorded first on one tape recorder, then the other tape recorder is brought into operation shortly before the end of first tape, so that there is some overlap to ensure continuous recording during a long recording session.

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