共查询到20条相似文献,搜索用时 31 毫秒
1.
Brown SW Johnson BC Biggar SF Zalewski EF Cooper J Hajek P Hildum E Grant P Barnes RA Butler JJ 《Applied optics》2005,44(30):6426-6443
The National Aeronautics and Space Administration's (NASA's) Ames Research Center's Airborne Sensor Facility (ASF) is responsible for the calibration of several airborne Earth-viewing sensor systems in support of NASA Earth Observing System (EOS) investigations. The primary artifact used to calibrate these sensors in the reflective solar region from 400 to 2500 nm is a lamp-illuminated integrating sphere source. In September 1999, a measurement comparison was made at the Ames ASF Sensor Calibration Facility to validate the radiometric scale, establish the uncertainties assigned to the radiance of this source, and examine its day-to-day repeatability. The comparison was one of a series of validation activities overseen by the EOS Calibration Program to ensure the radiometric calibration accuracy of sensors used in long-term, global, remote-sensing studies. Results of the comparison, including an evaluation of the Ames Sensor Calibration Laboratory (SCL) measurement procedures and assigned radiometric uncertainties, provide a validation of their radiometric scale at the time of the comparison. Additionally, the maintenance of the radiance scale was evaluated by use of independent, long-term, multiyear radiance validation measurements of the Ames sphere source. This series of measurements provided an independent assessment of the radiance values assigned to integrating sphere sources by the Ames SCF. Together, the measurements validate the SCF radiometric scale and assigned uncertainties over the time period from September 1999 through July 2003. 相似文献
2.
S. W. Brown J. P. Rice J. E. Neira B. C. Johnson J. D. Jackson 《Journal of research of the National Institute of Standards and Technology》2006,111(5):401-410
A common radiometric platform for the development of application-specific metrics to quantify the performance of sensors and systems is described. Using this platform, sensor and system performance may be quantified in terms of the accuracy of measurements of standardized sets of source distributions. The prototype platform consists of spectrally programmable light sources that can generate complex spectral distributions in the ultraviolet, visible and short-wave infrared regions for radiometric, photometric and colorimetric applications. In essence, the programmable spectral source is a radiometric platform for advanced instrument characterization and calibration that can also serve as a basis for algorithm testing and instrument comparison. 相似文献
3.
《IEEE sensors journal》2009,9(1):71-78
4.
This paper describes the development and evaluation of features and virtual sensors that form the basis of a methodology for detecting and diagnosing multiple-simultaneous faults in vapor compression air conditioning equipment. The features were developed based upon a physical understanding of the system, cost considerations, and heuristics derived from experimental data and modeling results. Virtual sensors were developed in order to reduce the cost of implementation. The validity of the features and virtual sensors was evaluated using measurements from a variety of different air conditioners tested in a laboratory environment. More detailed evaluation results are presented in separate papers. 相似文献
5.
《IEEE transactions on instrumentation and measurement》1969,18(3):172-183
Low-noise antenna systems are frequently used in conjunction with measurements of atmospheric and cosmic background noise at microwave frequencies. The input transmission line losses of these receiving systems must be precisely calibrated to insure proper identification of the portion of operating noise temperature attributable to the external environment. Although most components in an antenna line can be calibrated by conventional insertion-loss measurements, many feed component losses must be evaluated by means of nonstandard techniques. This paper describes a radiometric method for calibrating the loss of multimode antenna-feed components in which the field is linearly or circularly polarized. The method consists of measuring operating noise temperature, first with the components under evaluation installed and again after substitution by a waveguide section of known loss. Calibration and error analysis equations are derived and discussed. Application of the radiometric method, for the calibration of a mode-generator and quarter-wave plate polarizing section, resulted in a loss measurement of (0.0069 ±0.0016 pe)/dB. 相似文献
6.
N. Venkateswaran P. S. Goel M. S. Siva P. Natarajan E. Krishnakumar N. K. Philip 《Sadhana》2004,29(2):189-203
Remote sensing satellites are required to meet stringent pointing and drift rate requirements for imaging operations. For
achieving these pointing and stability requirements, continuous and accurate three-axis attitude information is required.
Inertial sensors like gyros provide continuous attitude information with better short-term stability and less random errors.
However, gyro measurements are affected by drifts. Hence over time, attitudes based on the gyro reference slowly diverge from
the true attitudes. On the other hand, line-of-sight (LOS) sensors like horizon sensors provide attitude information with
long-term stability. Their measurements however are affected by the presence of random instrumental errors and other systematic
errors. The limitations of inertial and line-of-sight sensors are mutually exclusive. Hence, by optimal fusion of attitude
information from both these sensors, it is possible to retain the advantages and overcome the limitations of both, thereby
providing the precise attitude information required for control.
This paper describes an improved earth-pointing scheme by fusion of the three-axis attitude information from gyros and horizon
sensor roll and pitch measurements along with yaw updates from the digital sun sensor. A Kalman Filter is used to estimate
the three-axis attitude by online estimation and corrections of various errors from the sensor measurements. Variations in
orbit rate components are also accounted for using spacecraft position and velocity measurements from the satellite positioning
system. Thus precise earth-pointing is achieved 相似文献
7.
Measuring absolute infrared spectral radiance with correlated visible photons: technique verification and measurement uncertainty 总被引:3,自引:0,他引:3
An experimental system in which correlated photons for radiometric measurements were used has been set up at the National Institute of Standards and Technology. We use visible-IR pairs of correlated photons produced by means of optical parametric downconversion to measure the radiance of a high-temperature IR source at 3.415 and 4.772 mum in an intrinsically absolute manner (i.e., without requiring any externally calibrated radiometric standard). To our knowledge, this is the only radiometric method with which one measures radiance directly, instead of using radiant power and aperture geometry measurements to deduce radiance indirectly. This technique has an additional unusual characteristic: It allows absolute radiometric measurements of IR radiation to be made with high-quality visible detectors. We compare measurements made with this technique with radiance measurements made with conventional means tied to existing radiometric standards. These comparisons show an average agreement to within ~3% between the two methods. The results demonstrate an accuracy consistent with the estimated uncertainty of the currentmeasurements. This is the first time to our knowledge that this method has been used to provide absolute radiance measurements of a source that has been calibrated conventionally, revealing unexpected systematic effects and allowing estimates of the ultimate accuracy of this method. In addition, these measurements are further into the IR than any previous measurements of this process and have produced the highest thermally stimulated downconversion signal yet seen. 相似文献
8.
E. R. Woolliams R. Winkler S. G. R. Salim P. M. Harris I. M. Smith 《International Journal of Thermophysics》2009,30(1):144-154
Filter radiometry provides thermodynamic temperatures traceable to a cryogenic radiometer. An alternative technique is possible
which provides absolute thermodynamic temperature through a different traceability chain, with the radiometric measurements
purely relative. If this technique could be experimentally realized with similar uncertainties to those associated with filter
radiometry, then this would provide a metrologically valuable ‘second opinion’ that would test for systematic effects common
to all filter radiometry measurements. This paper describes the theoretical analysis prior to an experimental investigation
of this technique. This theoretical analysis implies that with Re-C and Cu as the two blackbodies, the Re-C temperature can
be determined with an uncertainty of approximately twice that expected with filter radiometry. For higher-temperature metal-carbide/carbon
eutectics, the uncertainty difference would be smaller. 相似文献
9.
This paper describes a new computer-based gamma ray monitor for laboratory and field measurements. The monitor consists of a universal peripheral device, and GM counter gamma ray probe, connected via USB to the PC. The peripheral device is generic; in addition to the GM probe, it accepts sensors for spectrometric measurements as well as sensors for the measurement of other environmental parameters. Owing to its low-power consumption, it is used with laptop or palmtop computer, as a portable field measurement instrument. The proposed solution has advantages over conventional instrument: (1) open architecture; (2) user-defined functions and (3) easy network connection. 相似文献
10.
《IEEE sensors journal》2009,9(8):936-943
11.
H.C.H. Li I. Herszberg C.E. Davis A.P. Mouritz S.C. Galea 《Composite Structures》2006,75(1-4):321-327
This paper describes a methodology for the health monitoring of composite marine joint structures based on strain measurements under operational loading using embedded fibre Bragg grating sensors. Finite element modelling indicated that the presence of a disbond significantly altered the bond-line longitudinal strain distribution. This was verified qualitatively through an experimental test program. The experimental results are examined in relation to the FE predictions and the implications for a practical strain-based SHM system are discussed. A technique is developed, based on novel signal processing and statistical outlier detection. This enables the sensor measurements to be used for damage detection without reference to a high-fidelity numerical model of the structure which is often difficult and resource-intensive to generate. The technique is shown to provide successful damage diagnoses with an acceptable level of accuracy. Further improvement in diagnostic accuracy may be achieved by increasing the sensor density. 相似文献
12.
Catherine Cooksey Raju Datla 《Journal of research of the National Institute of Standards and Technology》2011,116(1):505-516
Detecting the small signals of climate change for the most essential climate variables requires that satellite sensors make highly accurate and consistent measurements. Data gaps in the time series (such as gaps resulting from launch delay or failure) and inconsistencies in radiometric scales between satellites undermine the credibility of fundamental climate data records, and can lead to erroneous analysis in climate change detection. To address these issues, leading experts in Earth observations from National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Adminstration (NOAA), United States Geological Survey (USGS), and academia assembled at the National Institute of Standards and Technology on December 10, 2009 for a workshop to prioritize strategies for bridging and mitigating data gaps in the climate record. This paper summarizes the priorities for ensuring data continuity of variables relevant to climate change in the areas of atmosphere, land, and ocean measurements and the recommendations made at the workshop for overcoming planned and unplanned gaps in the climate record. 相似文献
13.
Fault-tolerant sensor systems using evolvable hardware 总被引:7,自引:0,他引:7
This paper describes a system that is robust with respect to a sensor failure. The system utilizes multiple sensor inputs (three in this case) connected to a programmable device that averages the outputs from the sensors. The programmable device is programmed using evolvable hardware techniques. If one or more of the input sensors fail, then the controller detects the failure and initiates a reprogramming of the circuit. The system then continues to operate with a reduced number of sensors. The failure detection is accomplished by comparing the actual system output with a Kalman-filter estimate of the output. If the actual output and the filter estimate differ by an amount greater than the system uncertainty, then a failure is noted. The system is robust to several different failure modes: sensor fails as open circuit, sensor fails as short circuit, partial failures, multiple sensors fail, field programmable analog array input amplifier failure. This paper describes the experimental setup as well as results using actual temperature sensors. For all failure types, the system was able to recover to within 2% of the target value. 相似文献
14.
Krommenhoek EE Gardeniers JG Bomer JG Li X Ottens M van Dedem GW Van Leeuwen M van Gulik WM van der Wielen LA Heijnen JJ van den Berg AA 《Analytical chemistry》2007,79(15):5567-5573
This paper describes the design, modeling, and experimental characterization of an electrochemical sensor array for on-line monitoring of fermentor conditions in both miniaturized cell assays and in industrial scale fermentations. The viable biomass concentration is determined from impedance spectroscopy. As a miniaturized electrode configuration with high cell constant is applied, the spectral conductivity variation is monitored instead of the permittivity variation. The dissolved oxygen concentration is monitored amperometrically using an ultramicroelectrode array, which is shown to have negligible flow dependence. pH is monitored using an ion-sensitive field effect transistor (ISFET), and a platinum thermistor is included for temperature measurements. All sensors were shown to be sufficiently accurate within the range relevant to yeast fermentations. The sensor array is shown to be very stable and durable and withstands steam-sterilization. 相似文献
15.
Temperature correction of radiometric and geometric models for an uncooled CCD camera in the near infrared 总被引:1,自引:0,他引:1
Sentenac T. Le Maoultt Y. Rolland G. Devy M. 《IEEE transactions on instrumentation and measurement》2003,52(1):46-60
This paper presents radiometric and geometric models for both temperature and displacement noncontact measurements using an uncooled charge-coupled device (CCD) video camera. Such techniques ("one sensor-two measures") represent an interest in many industrial low cost applications and scientific domains. To benefit from both measurements, we have to use the camera's spectral response in the near infrared spectral band from 0.75 to 1.1 /spl mu/m. In this spectral band, the temperature variations of an uncooled CCD camera are taken into account in the radiometric and geometric models. By using physical models for CCD camera, we quantify detector's quantum efficiency, sensor noise and spatial resolution as a function of the wavelength and of the detector temperature. These models are confirmed by experimental results of calibration with a low cost uncooled camera based on a Sony detector and operating over the detector temperature range of -30 to -50/spl deg/. 相似文献
16.
Calibration of SeaWiFS. I. Direct techniques 总被引:1,自引:0,他引:1
We present an overview of the calibration of the Sea-viewing Wide Field-of View Sensor (SeaWiFS) from its performance verification at the manufacturer's facility to the completion of its third year of on-orbit measurements. These calibration procedures have three principal parts: a prelaunch radiometric calibration that is traceable to the National Institute of Standards and Technology; the Transfer-to-Orbit Experiment, a set of measurements that determine changes in the instrument's calibration from its manufacture to the start of on-orbit operations; and measurements of the sun and the moon to determine radiometric changes on orbit. To our knowledge, SeaWiFS is the only instrument that uses routine lunar measurements to determine changes in its radiometric sensitivity. On the basis of these methods, the overall uncertainty in the SeaWiFS top-of-the-atmosphere radiances is estimated to be 4-5%. We also show the results of comparison campaigns with aircraft- and ground-based measurements, plus the results of an experiment, called the Southern Ocean Band 8 Gain Study. These results are used to check the calibration of the SeaWiFS bands. To date, they have not been used to change the instrument's prelaunch calibration coefficients. In addition to these procedures, SeaWiFS is a vicariously calibrated instrument for ocean-color measurements. In the vicarious calibration of the SeaWiFS visible bands, the calibration coefficients are modified to force agreement with surface truth measurements from the Marine Optical Buoy, which is moored off the Hawaiian Island of Lanai. This vicarious calibration is described in a companion paper. 相似文献
17.
A Chemical Nuclear Reconnaissance System (CNRS) has been developed by the British Ministry of Defence to make chemical and radiation measurements on contaminated terrain using appropriate sensors and recording equipment installed in a land rover. A research programme is under way to develop and validate a predictive capability to calculate the build-up of contamination on the vehicle, radiation detector performance and dose rates to the occupants of the vehicle. This paper describes the geometric model of the vehicle and the methodology used for calculations of detector response. Calculated dose rates obtained using the MCBEND Monte Carlo radiation transport computer code in adjoint mode are presented. These address the transient response of the detectors as the vehicle passes through a contaminated area. Calculated dose rates were found to agree with the measured data to be within the experimental uncertainties, thus giving confidence in the shielding model of the vehicle and its application to other scenarios. 相似文献
18.
This paper describes a novel design for capacitive sensors or chemical sensors, which features configurable interdigitated electrodes: The electrode spacing can be varied by means of switches on the CMOS chip. This new design allows for performing two capacitive measurements with one single-sensor capacitor so that the number of sensors required to acquire a certain amount of information can be significantly reduced. The use of the same sensor and the same polymer layer for two measurements at a different electrode periodicity provides a better signal quality for the difference signal since detrimental influences, such as humidity and sensor drift, are similar for both electrode configurations and are strongly correlated. Such high signal quality is required for, e.g., the successful recognition of n-octane in the presence of tenfold larger background signals of humidity or, in general, for the determination of low analyte concentrations in humid air. The baseline drift in the concentration predictions based on the differential signal from the two electrode configurations was an order of magnitude lower than that for uncorrelated signals produced by two separate interdigitated capacitors on the same chip. Since the number of required sensors is reduced and, owing to the differential readout of two electrode configurations, reference capacitors are no longer necessary, the overall chip size and/or the number of sensor chips and, consequently, costs can be considerably reduced. 相似文献
19.
This paper concerns the Fourier analysis of measurements taken at times that are not at all uniformly spaced yet are accurately known. Such can be the case when measurements are obtained by networked sensors with accurate or synchronized clocks using common Internet Protocol networks or other networks that do not guarantee timely data delivery. Such can also be the case when the object being measured is only sporadically available for measurement. A method for computing a complex spectrum from a minimal number of samples taken at nonuniform time intervals is described. The novelty of this paper lies in the method's ability to minimize the number of samples required to ensure a desired accuracy. A practical application of the method lies in doing spectral analysis of signals obtained from networked sensors where acquiring each sample is expensive in time, power, or money, and so, the number of samples taken is to be minimized. The method has been tested on two rather different sets of actual measurements: one taken via smart sensors connected to the Internet and the other taken by a number of observational astronomers using a variety of apparatus over decades. 相似文献
20.
The non-contact measurement of temperature by using the emitted thermal radiation has been an innovative field of measurement
science and fundamental physics for more than a hundred years. It saw the first highlight in Gustav Kirchhoff’s principle
of a blackbody with ideal emission characteristics and culminated in Max Planck’s formulation of the law of thermal radiation,
the so-called Planck’s law, forming the foundation of quantum physics. A boost in accuracy was the development of semiconductor
detectors and the cryogenic electrical substitution radiometer in the late 1970s. Semiconductor detectors, namely photodiodes,
deliver an electrical current proportional to the absorbed optical radiation. Due to the measurements of thermal radiation
over a wide range of temperature and wavelength, thermodynamic temperature measurements with radiometric methods have set
benchmarks to all, the electrical, dimensional and optical metrology. The paper describes the measurement of the spectral
responsivity of semiconductor detectors traceable to the SI units and their application for thermodynamic temperature measurement
by the absolute measurement of thermal radiation using filter radiometers with calibrated spectral irradiance responsivity. 相似文献