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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 1,099 records · Page 61

All sources NASA NTRS DOE OSTI

NASA NTRS1976

Ultrasonic evaluation of high voltage circuit boards

Preliminary observations indicate that an ultrasonic scanning technique may be useful as a quick, low cost, nondestructive method for judging the quality of circuit board materials for high voltage applications. Corona inception voltage tests were conducted on fiberglass-epoxy and fiberglass-polyimide high pressure laminates from 20 to 140 C. The same materials were scanned ultrasonically by utilizing the single transducer, through-transmission technique with reflector plate, and recording variations in ultrasonic energy transmitted through the board thickness. A direct relationship was observed between ultrasonic transmission level and corona inception voltage. The ultrasonic technique was subsequently used to aid selection of high quality circuit boards for the Communications Technology Satellite.

Klima, S. J.↗

NASA NTRS1976

A parylene coating process for hybrid circuits

The parylene coating process developed during this program consists of (1) obtaining a hybrid cover with a hole in it, (2) sealing of the circuit with a hole in the cover, (3) parylene coating through the hole with the external leads protected from parylene by appropriate fixturing, and (4) sealing of the hole by soldering a pretinned kovar tab. Development of the above process required optimization of the parylene coater parameters to obtain a uniform consistent coating which could offer adequate protection to the circuits, fixture design for packages of various types, determination of the size of the deposition hole, and the amount of dimer charge per run, a process to hermetically seal the deposition holes and establishment of quality control techniques or acceptance criteria for the deposited film.

Source record↗

NASA NTRS1977

Factors affecting the open-circuit voltage and electrode kinetics of some iron/titanium redox flow cells

Performance of the iron-titanium redox flow cell was studied as a function of acid concentration. Anion permeable membranes separated the compartments. Electrodes were graphite cloth. Current densities ranged up to 25 mA/square centimeter. Open-circuit and load voltages decreased as the acidity was increased on the iron side as predicted. On the titanium side, open-circuit voltages decreased as the acidity was increased in agreement with theory, but load voltages increased due to decreased polarization with increasing acidity. High acidity on the titanium side coupled with low acidity on the iron side gives the best load voltage, but such cells show voltage losses as they are repeatedly cycled. Analyses show that the bulk of the voltage losses are due to diffusion of acid through the membrane.

Reid, M. A.↗

NASA NTRS1977

Semicustom integrated circuits and the standard transistor array radix (STAR)

The development, application, pros and cons of the semicustom and custom approach to the integration of circuits are described. Improvements in terms of cost, reliability, secrecy, power, and size reduction are examined. Also presented is the standard transistor array radix, a semicustom approach to digital integrated circuits that offers the advantages of both custom and semicustom approaches to integration.

Edge, T. M.↗

NASA NTRS1976

Clearance of short circuited ion optics electrodes by capacitive discharge

The ion optics electrodes of low specific impulse (3000 sec) mercury electron bombardment ion thrusters are vulnerable to short circuits by virtue of their relatively small interelectrode spacing (0.5 mm). Metallic flakes from backsputtered deposits are the most probable cause of such 'shorts' and 'typical' flakes have been simulated here using refractory wire that has a representative, but controllable, cross section. Shorting wires can be removed by capacitive discharge without significant damage to the electrodes. This paper describes an evaluation of 'short' removal versus electrode damage for several combinations of capacitor voltage, stored energy, and short circuit conditions.

Poeschel, R. L.↗

NASA NTRS1976

Ultrasonic evaluation of high voltage circuit boards

Klima, S. J.↗

NASA NTRS1978

Synchronous transfer circuits for redundant systems

Circuit arrangements for flip-flops, counters, and clock drivers in redundant systems ensure that control is synchronously transferred to surviving components when failure occurs. In addition to original application to spacecraft systems, redundant circuits have terrestrial uses in power generators, solar-energy converters, computers, vehicle controllers, and other systems demanding high reliability.

Nagano, S.↗

NASA NTRS1979

Simple digital pulse-programing circuit

Pulse-sequencing circuit uses only shift register and Exclusive-OR gates. Circuit also serves as date-transition edge detector (for rising or falling edges). It is used in sample-and-hold, analog-to-digital conversion sequence control, multiphase clock logic, precise delay control computer control logic, edge detectors, other timing applications, and provides simple means to generate timing and control signals for data transfer, addressing, or mode control in microprocessors and minicomputers.

Langston, J. L.↗

NASA NTRS1979

Testing integrated circuits by photoexcitation

System for testing integrated circuits uses photoexcitation to determine quality of internal elements inaccessible to electrical tests. Approach prevents direct monitoring of internal operation of circuit by measurements at external terminals and is superior to electron beam scanning due to nondestructiveness.

Erickson, J. J.↗

NASA NTRS1979

Hybrid temperature-monitoring circuit

Hybrid circuit developed for use in hand-held vital signs monitor converts resistance of thermistor probe to 3 1/2 digit BCD (binary-coded-decimal) temperature readout. If used alone circuit can form 'stand alone' temperature monitor or can transmit temperature data via telemetry to data acquisition systems.

Rinard, G. A.↗

NASA NTRS1977

Frequency method for determining the parameters of the electromagnetic brakes and slip-type couplings with solid magnetic circuits

The equivalent representation of brakes and coupling by lumped circuits is investigated. Analytical equations are derived for relating the indices of the transients to the parameters of the equivalent circuits for arbitrary rotor speed. A computer algorithm is given for the calculations.

Guseynov, F. G.↗

NASA NTRS1977

Measurement of material parameters that limit the open-circuit voltage in P-N-junction silicon solar cells

The greatest gains in solar energy conversion efficiency of p-n-junction silicon solar cells come from increasing the open-circuit voltage V sub OC; it is important to understand and characterize the material parameters that limit the V sub OC. Strong experimental evidence exists to support the assertion that either an anomalously large minority carrier charge storage or an anomalously small minority carrier lifetime in the quasi-neutral emitter region limits the open circuit voltage. A method is presented for measuring charge storage and effective lifetime. Static and transient measurements are analyzed using physical models of the solar cell characteristics. This analysis yields the emitter charge storage and life-time, which then can be related to the various physical mechanisms, such as energy band gap shrinkage, that have been proposed earlier as responsible for limiting V sub OC.

Lindholm, F. A.↗

NASA NTRS1977

Integrated circuit process and design rule evaluation techniques

A technique is described for determining the applicability of a particular process for the fabrication of large-scale integrated (LSI) circuits. Test arrays were developed to isolate various critical processing steps in a fabrication sequence and a statistical evaluation of these steps was carried out that related yield or success in achieving a desired result to the number of times the results were attempted. It was found that, in general, yield is a sensitive function of physical dimensions as is the packing density of a particular array. It is, therefore, possible to generate an optimum set of physical dimensions or design rules that maximize the expected number of working circuits on a wafer.

Ipri, A. C.↗

NASA NTRS1979

CMOS circuit-fabrication handbook

Report describes complementary metal-oxide-semiconductor (CMOS) process used to fabricate integrated circuits at Marshall Space Flight Center. It also presents general discussions of circuit design, mask making packaging, and testing.

Bouldin, D. L.↗

NASA NTRS1980

Minimizing spikes in switching-regulator circuits

Circuit, employing tapped inductor to back-bias rectifying diodes and extra diode to cummutate current, minimizes current spikes that cause premature transistor failure in switching-regulator circuits.

Mclyman, W. T.↗

NASA NTRS1980

Detector verifier for circuit analyzers

Economical tool checks operation of automatic circuit analyzer. Each loop is addressed directly from analyzer console by switching internal analyzer bridge to resistance equal that of connecting cable plus specified limiting test value. Procedure verifies whether detected faults in circuit under test are actually due to analyzer malfunction. Standard-length universal test cables make it possible to shift detector tool from cable to cable without resistance compensation.

Pope, D. L.↗

NASA NTRS1978

Apparatus including a plurality of spaced transformers for locating short circuits in cables

A cable fault locator is described for sensing faults such as short circuits in power cables. The apparatus includes a plurality of current transformers strategically located along a cable. Trigger circuits are connected to each of the current transformers for placing a resistor in series with a resistive element responsive to an abnormally high current flowing through that portion of the cable. By measuring the voltage drop across the resistive element, the location of the fault can be determined.

Cason, R. L.↗

NASA NTRS1980

Multichannel coincidence circuit

Digital circuit detects coincident pulses in two or more channels, and records time between primary pulses that are coincident with secondary pulses. Circuit has three major blocks: interval time subcircuit, measurement control subcircuit, and time sequence generator. Timer can be used in laser velocimeter or other instruments receiving data at irregular rates from two or more sources.

Clemmons, J. I., Jr.↗