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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The influence of a voltage ramp on the measurement of I-V characteristics of a solar cell

For efficiency and convenience the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a common rate of 1 V per millisecond. During this time the values of current are determined as a function of the instantaneous voltage thus producing an I-V characteristic. The present paper shows that the customary expressions for the current as a function of cell parameters still remain valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L1 given by L1 = L(1 + qV/kT.tau) to the -1/2, where V is the ramp rate considered constant and tau is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.

Von Roos, O.↗
NASA NTRS1990

MIS capacitor studies on silicon carbide single crystals

Cubic SIC metal-insulator-semiconductor (MIS) capacitors with thermally grown or chemical-vapor-deposited (CVD) insulators were characterized by capacitance-voltage (C-V), conductance-voltage (G-V), and current-voltage (I-V) measurements. The purpose of these measurements was to determine the four charge densities commonly present in an MIS capacitor (oxide fixed charge, N(f); interface trap level density, D(it); oxide trapped charge, N(ot); and mobile ionic charge, N(m)) and to determine the stability of the device properties with electric-field stress and temperature. The section headings in the report include the following: Capacitance-voltage and conductance-voltage measurements; Current-voltage measurements; Deep-level transient spectroscopy; and Conclusions (Electrical characteristics of SiC MIS capacitors).

Kopanski, J. J.↗
DOE OSTI2021

A Low Cost SIPM Evaluation and Control Prototyping System including accurate bias voltage generation, leakage current measurement, and temperature control using Peltier cooling

We describe an electronics system to operate SIPMs in the laboratory. The system is comprised of a single channel amplifier board (SIPM Amp) and a 4-channel control board to which up to 4 SIPM Amp boards can be connected. The control board supplies a common low voltage power for the amplifiers. All channels feature individually regulated bias and Peltier power voltages, along withPt10K RTD readout. A graphical user interface allows control of the bias voltages, amplifier voltage, Peltier voltages, and also provides for readback of leakage currents and other voltages. The GUI app has a feedback loop to measure the SIPM temperature (with the PT10K) and generate correction voltages to the Peltier to regulate the temperature. The temperatures, which can be achieved by Peltier cooling depend on the thermal design of the setup, the practical limit being about 50C below ambient. The SIPM Amp. board is a small (3x5cm) PCB that has a single SIPM readout channel. The SIPM scan be surface mounted on the pcb or connected to a 2-pin 0.100" socket. The area around the SIPM footprint is thermally isolated by perforations in the PCB. The RTD is located inside the thermal break. Onboard is BV and LV filtering. The 10X amplifier is based on MiniCircuits' GALI-S66+ integrated circuit, tweaked for a 6V power. The amplifier was selected for a combination of high bandwidth, low noise, and low power. An accoupled amplifier output is connected to an SMA connector. For best operation of this inverting amplifier the output signal should be in the range of 0 to -1V.The Amplifier board is connected to the Control board with a 10-conductor 0.025" pitch ribbon cable, carrying all the services. Peltier power for currents more than 1A should use a separate 2-contact connector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1992

Electro-Optical High-Voltage Sensors

Electro-optical sensors for measuring high voltages developed for use in automatically controlled power-distribution systems. Sensors connected to optoelectronic interrogating equipment by optical fibers. Because sensitive material and optical fibers are all dielectric, no problem in electrically isolating interrogating circuitry from high voltage, and no need for voltage dividers. Sensor signals transmitted along fibers immune to electromagnetic noise at radio and lower frequencies.

Gottsche, Allan↗
NASA NTRS1976

LaF3 infrared detector

A class of infrared detectors is proposed, and experimental results are presented for a prototype device. The material used is LaF3, an ionic conductor with a capacitance that varies exponentially with temperature. The detectivity of a prototype detector is estimated from measured signal voltages and incident power, and a Johnson noise voltage is calculated from the measured resistance. At a modulation frequency of 20 Hz, the estimated detectivity is about 2 million cm/sq root Hz/W. For the parameters characterizing this device, the estimated detectivity is consistent with a theoretical prediction. The theory further predicts an optimum detectivity of about 1 billion cm/sq root Hz/W for much thinner devices than the prototypes.

Sher, A.↗
NASA NTRS2005

Thin-Film Resistance Heat-Flux Sensors

Thin-film heat-flux sensors of a proposed type would offer advantages over currently available thin-film heat flux sensors. Like a currently available thin-film heat-flux sensor, a sensor according to the proposal would be based on measurement of voltages related to the temperatures of thin metal films on the hotter and colder faces of a layer of an electrically insulating and moderately thermally conductive material. The heat flux through such a device is proportional to the difference between the temperatures and to the thermal conductivity of the layer. The advantages of the proposed sensors over the commercial ones would arise from the manner in which the temperature-related voltages would be generated and measured.

Fralick, Gustave C.↗
NASA NTRS2010

l/f Noise in the Superconducting Transition of a MgB2 Thin Film

The noise voltage spectral density in the superconducting transition of a MgB2 thin film on a SiN-coated Si thick substrate was measured over the frequency range 1 Hz-to-1 KHz. Using established bolometer noise theory the theoretical noise components due to Johnson, 1/f(excess) and phonon noise are modeled to the measured data. It is shown that for the case of a MgB2 thin film in the vicinity of the mid-point of transition, coupled to a heat sink via a fairly high thermal conductance (approximately equal to 10(sup -1) W/K)) that the measured noise voltage spectrum is 1/f limited and exhibits lit dependence with a varying between 0.3 and 0.5 in the measured frequency range. At a video frame rate frequency of 30 Hz the measured noise voltage density in the film is approximately equal to 61 nV /the square root of HZ, using this value an upper limit of electrical NEP approximately equal to 0.67pW / the square root of Hz is implied for a practical MgB2 bolometer operating at 36.1 K.

Lakew, B.↗
NASA NTRS1976

Metal-insulator-semi-conductor studies of lead telluride

The capacitance and conductance-voltage characteristics were measured on metal-insulator-semiconductor capacitors fabricated with zirconium dioxide films on single-crystal lead telluride. At 77 K, on both n- and p-type substrates, evidence of surface potential control was obtained. Comparison of the measured capacitance-voltage characteristics with those calculated from the equilibrium solution of the one-dimensional Poisson equation indicated qualitative agreement, although the slope of the measured capacitance in the region near the capacitance minimum was less steep than calculated.

Lilly, D. A.↗
NASA NTRS1983

Ambient and cryogenic temperature testing of a 32-channel CMOS multiplexer

A 32 channel CMOS multiplexer was tested at room temperature and at liquid helium temperature (4.9 K). Voltage gain of the FET input stage, leakage current, electrical crosstalk, and noise as a function of clock frequency were measured. The voltage gain measured at 4.9 K was slightly higher than that measured at 300 K and was independent of clock frequency at both operating temperatures. The off channel leakage current was 0.23 pA/channel at 4.9 K. Electrical crosstalk between adjacent channels (one on, one off) was quite low. The spot noise at 10 Hz, of the CMOS multiplexer operating in the static mode did not vary significantly with operating temperature. In the dynamic mode (3.2 kHz clock) at room temperature, the spot noise at 10 Hz was substantially higher than that measured in the static mode.

Lee, J. H.↗
NASA NTRS1978

Summary of system state-of-health measurements STRATCOM 8: A balloon experiment

Various measurements were made to determine the temperature and attitude of the gondola and the status of primary power and control equipment. Bead thermistors were used to measure temperatures at selected points throughout the gondola. A two-axis magnetometer and a two-axis pendulum were used to measure gondola attitude. Voltage and current measurements indicated the status of the primary power sources and associated power converters.

Herrington, P. B.↗
NASA NTRS2000

Microwave Driven Actuators Power Allocation and Distribution

Design, fabrication and test of a power allocation and distribution (PAD) network for microwave driven actuators is presented in this paper. Development of a circuit that would collect power from a rectenna array amplify and distribute the power to actuators was designed and fabricated for space application in an actuator array driven by a microwave. A P-SPICE model was constructed initially for data reduction purposes, and was followed by a working real-world model. A voltage up - converter (VUC) is used to amplify the voltage from the individual rectenna. The testing yielded a 26:1 voltage amplification ratio with input voltage at 9 volts and a measured output voltage 230VDC. Future work includes the miniaturization of the circuitry, the use of microwave remote control, and voltage amplification technology for each voltage source. The objective of this work is to develop a model system that will collect DC voltage from an array of rectenna and propagate the voltage to an array of actuators.

Forbes, Timothy↗
DOE OSTI2023

Medium-Voltage Testbed for Comparing Advanced Power Line Sensors vs. Measurement Transformers with Electrical Grid Events

Electrical utilities have relied upon potential transformers (PTs) and current transformers (CTs) for very accurate metering and to provide reliable signals for protective relays. Less expensive alternative sensing technologies offer the possibility of wider deployment, particularly in grids that employ distributed energy resources. In this work, the performance of an advanced medi-um-voltage sensor is compared with a reference PT and CT and experimentally evaluated for different power grid scenarios on an advanced outdoor power line sensor testbed at the US De-partment of Energy’s Oak Ridge National Laboratory. The sensor is based on a capacitive divider for voltage monitoring and a Rogowski coil with integrator for current monitoring. The advanced outdoor power line sensor testbed has a real-time simulator that was used to generate transient scenarios (e.g., electrical faults, capacitor bank operation, service restoration), while the analog signals were recorded by the same high resolution power meter. The behavior of analog signals, harmonic components, total harmonic distortion, and crest factors were assessed for this power line sensor compared with the reference PT/CT, because of the absence for testing standards for advanced outdoor power line sensors.

Piesciorovsky, Emilio↗
NASA NTRS1981

Analysis of the photo voltage decay /PVD/ method for measuring minority carrier lifetimes in P-N junction solar cells

The photo voltage decay (PVD) method for the measurement of minority carrier lifetimes in P-N junction solar cells with cell thickness comparable to or even less than the minority carrier diffusion length is examined. The method involves the generation of free carriers in the quasi-neutral bulk material by flashes of light and the monitoring of the subsequent decay of the induced open-circuit voltages as the carriers recombine, which is dependent on minority carrier recombination lifetime. It is shown that the voltage versus time curve for an ordinary solar cell (N(+)-P junction) is proportional to the inverse minority carrier lifetime plus a factor expressing the ratio of diffusion length to cell thickness. In the case of an ideal back-surface-field cell (N(+)-P-P(+) junction) however, the slope is directly proportional to the inverse minority carrier lifetime. It is noted that since most BSF cells are not ideal, possessing a sizable back surface recombination velocity, the PVD measurements must be treated with caution and supplemented with other nonstationary methods.

Von Roos, O.↗
DOE OSTI2023

Electrostatic charge buildup and electrostatic discharge monitoring system and method

A system for monitoring electrostatic charge buildup and electrostatic discharge (ESD) remotely comprises a plurality of electrostatic charge measurement units and a data acquisition device. Each electrostatic charge measurement unit includes a primary charge plate, a static sensor device, a secondary charge plate, and a shielded cable. The primary charge plate is positioned proximal to an object. The static sensor device includes an input sensor at which an electric voltage is measured and outputs an electronic signal whose level varies according to the measured electric voltage. The secondary charge plate is positioned in proximity to the input sensor of the static sensor device. The shielded cable includes an inner conductor electrically connected to the primary charge plate and the secondary charge plate and an outer conductor electrically connected to electrical ground. The data acquisition device receives the electronic signal from the static sensor device of each electrostatic charge measurement unit.

Schantz, Eric T.↗
DOE OSTI2023

Voltage-Based Strategies for Preventing Battery Degradation under Diverse Fast-Charging Conditions

Maintaining safe operating conditions is a key challenge for high-performance lithium-ion battery applications. The lithium-plating reaction remains a risk during charging, but limited studies consider the highly variable charging conditions possible in commercial cells. Here we combine pseudo-2D electrochemical modeling with data visualization methods to reveal important relationships between the measurable cell voltage and difficult-to-predict Li-plating onset criteria. An extensively validated model is used to compute Li plating for thousands of multistep charging conditions spanning diverse rates, temperatures, states-of-charge, and cell aging. Here we observe an empirical cell operating voltage limit below which plating does not occur across all conditions, and this limit varies with the battery state-of-charge and aging. A model sensitivity analysis also indicates that, when comparing two charging voltage profiles, the capacity difference at 4.0 V correlates well with the difference in the plating onset capacity. These results encourage simple strategies for Li-plating prevention that are complementary to existing battery controls.

25 ENERGY STORAGE↗