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Results for “resistivity measurements”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Four-terminal connector for measuring resistance of a pyrotechnic initiator

A four-terminal electrical connector device (40) for testing and measuring unknown resistances of initiators (11) used for starting pyrotechnic events aboard a Space Transportation System. The testing device minimizes contact resistance degradation effects and so improves the reliability of resistance measurement taken with the device. Separate and independent voltage sensing (19) and current supply (20) circuits each includes a pair of socket contacts (13-16) for mating engagement with the pins (17,18) of the initiator. The unknown resistance that is measured by the device is the resistance of the bridgewire (23) of the initiator which is required to be between 0.95 and 1.15 ohms.

Robinson, Robert L.↗
NASA NTRS1970

A Study of the Electrotransport in Thin Films: An Advanced Method for the Study of Electrotransport in Thin Films Using Electrical Resistance Measurements

To date, very little is understood about electrotransport in thin films. One reason for this is the lack of methods in which electromigration can be adequately monitored dynamically. In this thesis, a new nondestructive method for the study of the electrotransport phenomenon in thin aluminum films is presented. This method makes use of electrical resistance measurements of various regions along the test sample to monitor changes in resistance resulting from electromigration. The advantage of this method is that resistance changes can be observed long before void formation can be seen using standard microscopy methods. In order to achieve the best efficiency using this method, special consideration must be given to the design of the sample. Design problems and their respective solutions are given. The results of the electrical resistance measurements are interpreted by means of photographs taken with an scanning electron microscope. The increase in resistance of the aluminum samples is interpreted to be due to void formation. The expected decrease in resistance near the anode was never observed. It is shown that mass accumulation takes on the form of hillocks and whiskers on the surface of the aluminum film, which does not contribute appreciably to conductivity.

Hummel, R. E.↗
NASA NTRS2020

High-Resistivity Measurement System for Spacecraft Dielectrics

- Volume resistivity is a key material property needed for assessing the risk of electrostatic discharge (ESD) due to spacecraft charging. We have developed a volume resistivity test system capable of measuring volume resistivity ≥1019 Ω·cm in vacuum and at cryogenic temperatures. Key components of this new setup include a custom test fixture and very low noise battery voltage supply.

Chave, Robert↗
NASA NTRS1976

Contactless method of measuring resistivity

A method is described for measuring the conductivity of materials without having to make electrical contact with the material. Currents which are magnetically induced in the conducting sample are measured by means of the magnetic fields they produce. Although induction techniques have been used in the past for this type of measurement, the configuration presented here makes it possible to perform absolute measurements of resistivity over a wide range of values for relatively small samples. The theory of the technique, the results of measurements made with it, and a comparison of the technique with other methods are presented.

Crowley, J. D.↗
NASA NTRS1986

Measuring Resistivities of Small Fibers

Technique for measuring electrical resistivities of fibers of graphite, silicon carbide/silicon nitride mixture, and other materials used in composites simple, accurate, and reproducible. Suitable for monofilament fibers with diameters of about 10 to 50 micrometers. Also adapted to two fiber strands.

Daniels, J.↗
NASA NTRS1968

Resistivity measurements of neutron-irradiated pure metals and Al-Zn alloys

Report presents resistivity measurements and their interpretation for neutron-irradiated pure metals and Al-Zn alloys. The influence of temperature, the role of point defects, and the aging behavior on resistivity are considered. The experimental procedures and results are discussed in detail.

Horak, J. A.↗
NASA NTRS2005

Proposed Modifications to Engineering Design Guidelines Related to Resistivity Measurements and Spacecraft Charging

A key parameter in modeling differential spacecraft charging is the resistivity of insulating materials. This determines how charge will accumulate and redistribute across the spacecraft, as well as the time scale for charge transport and dissipation. Existing spacecraft charging guidelines recommend use of tests and imported resistivity data from handbooks that are based principally upon ASTM methods that are more applicable to classical ground conditions and designed for problems associated with power loss through the dielectric, than for how long charge can be stored on an insulator. These data have been found to underestimate charging effects by one to four orders of magnitude for spacecraft charging applications. A review is presented of methods to measure the resistive of highly insulating materials, including the electrometer-resistance method, the electrometer-constant voltage method, the voltage rate-of-change method and the charge storage method. This is based on joint experimental studies conducted at NASA Jet Propulsion Laboratory and Utah State University to investigate the charge storage method and its relation to spacecraft charging. The different methods are found to be appropriate for different resistivity ranges and for different charging circumstances. A simple physics-based model of these methods allows separation of the polarization current and dark current components from long duration measurements of resistivity over day- to month-long time scales. Model parameters are directly related to the magnitude of charge transfer and storage and the rate of charge transport. The model largely explains the observed differences in resistivity found using the different methods and provides a framework for recommendations for the appropriate test method for spacecraft materials with different resistivities and applications. The proposed changes to the existing engineering guidelines are intended to provide design engineers more appropriate methods for consideration and measurements of resistivity for many typical spacecraft charging scenarios.

Dennison, J. R.↗
NASA NTRS1986

Method for contact resistivity measurements on photovoltaic cells and cell adapted for such measurement

A method is disclosed for scribing at least three grid contacts of a photovoltaic cell to electrically isolate them from the grid contact pattern used to collect solar current generated by the cell, and using the scribed segments for determining parameters of the cell by a combination of contact end resistance (CER) measurements using a minimum of three equally or unequally spaced lines, and transmission line modal (TLM) measurements using a minimum of four unequally spaced lines. TLM measurements may be used to determine sheet resistance under the contact, R.sub.sk, while CER measurements are used to determine contact resistivity, .rho..sub.c, from a nomograph of contact resistivity as a function of contact end resistance and sheet resistivity under the contact. In some cases, such as the case of silicon photovoltaic cells, sheet resistivity under the contact may be assumed to be equal to the known sheet resistance, R.sub.s, of the semiconductor material, thereby obviating the need for TLM measurements to determine R.sub.sk.

Burger, Dale R.↗