Calibration Setup Research Articles

Derivation of an urban materials spectral library through emittance and reflectance spectroscopy

Recent advances in thermal infrared remote sensing include the increased availability of airborne hyperspectral imagers (such as the Hyperspectral Thermal Emission Spectrometer, HyTES, or the Telops HyperCam and the Specim aisaOWL), and it is planned that an increased number spectral bands in the long-wave infrared (LWIR) region will soon be measured from space at reasonably high spatial resolution (by imagers such as HyspIRI). Detailed LWIR emissivity spectra are required to best interpret the observations from such systems. This includes the highly heterogeneous urban environment, whose construction materials are not yet particularly well represented in spectral libraries. Here, we present a new online spectral library of urban construction materials including LWIR emissivity spectra of 74 samples of impervious surfaces derived using measurements made by a portable Fourier Transform InfraRed (FTIR) spectrometer. FTIR emissivity measurements need to be carefully made, else they are prone to a series of errors relating to instrumental setup and radiometric calibration, which here relies on external blackbody sources. The performance of the laboratory-based emissivity measurement approach applied here, that in future can also be deployed in the field (e.g. to examine urban materials in situ), is evaluated herein. Our spectral library also contains matching short-wave (VIS–SWIR) reflectance spectra observed for each urban sample. This allows us to examine which characteristic (LWIR and) spectral signatures may in future best allow for the identification and discrimination of the various urban construction materials, that often overlap with respect to their chemical/mineralogical constituents. Hyperspectral or even strongly multi-spectral LWIR information appears especially useful, given that many urban materials are composed of minerals exhibiting notable reststrahlen/absorption effects in this spectral region. The final spectra and interpretations are included in the London Urban Micromet data Archive (LUMA; http://LondonClimate.info/LUMA/SLUM.html).

New Fast Response Thin Film-Based Superconducting Quench Detectors

Quench detection on superconducting bus bars and other devices with a low normal zone propagation velocity and low voltage build-up is quite difficult with conventional quench detection techniques. Currently, on ATLAS superconducting bus bar sections, superconducting quench detectors (SQD) are mounted to detect quench events. A first version of the SQD essentially consists of an insulated superconducting wire glued to a superconducting bus line or windings, which in the case of a quench rapidly builds up a relatively high resistance that can be easily and quietly detected. We now introduce a new generation of drastically improved SQDs. The new version makes the detection of quenches simpler, more reliable, and much faster. Instead of a superconducting wire, now a superconducting thin film is used. The layout of the sensor shows a meander like pattern that is etched out of a copper coated 25 μm thick film of Nb-Ti glued in between layers of Kapton. Since the sensor is now much smaller and thinner, it is easier to install and build up a high resistance with a much shorter response time. The design of the sensors is explained. The test results of the new sensors in a few variants in a calibration setup as well as when mounted on the windings surface of a magnet are reported.

The spatial distribution of thermal and epithermal neutrons in a graphite moderated spallation neutron field

The Gamma-3 assembly is located at the Joint Institute for Nuclear Research, Dubna, Russia. It consists of a cylindrical lead target (ø = 8 cm, L = 58.8 cm) surrounded by reactor grade graphite (110 × 110 × 60 cm). The target was irradiated with a beam of 1.6 GeV deuterons from the Nuclotron accelerator and CR-39 track detectors coupled to LR-115 2B film were used to measure the slow neutron distribution on the surface of the graphite. The detection efficiency of the CR-39 in the CR-39/LR-115 2B system was measured using a custom made calibration setup and found to be (1.12 ± 0.05) × 10−3 and (6.1 ± 1.2) × 10−4 tracks per neutron, for thermal and epithermal neutrons respectively, under the etching and counting procedures described in this work. The irradiation of the Gamma-3 was also simulated using MCNPX 2.7 Monte Carlo code and good agreement between the experimental and calculated track densities was found. This serves as a good validation for the computational models used to simulate spallation neutron production, transport and moderation.

Validation of short-pulse-laser-based measurement setup for absolute spectral irradiance responsivity calibration.

This paper describes the validation process of mode-locked lasers in the "tunable lasers in photometry" (TULIP) setup at Physikalisch-Technische Bundesanstalt (PTB) regarding spectral irradiance responsivity calibrations. Validation has been carried out in the visible spectral range, 400-700 nm, with two different photometer heads and in the long wavelength range, 690-780 nm, with a filtered radiometer. A comparison of the results against those from two different validated measurement setups has been carried out for validation. For the visible spectral range, the comparison is conducted against the data obtained from a lamp-based monochromator setup for spectral irradiance responsivity calibrations and against the photometric values (integral quantity) measured at the photometric bench setup of PTB. For the long wavelength range, comparisons against results from two different lamp-based monochromator measurement setups were made. Additionally, the effect of different radiation bandwidths on interference oscillations has been determined for a filter radiometer without a diffuser. A procedure for the determination of the optimum bandwidth of the setup for the respective measurement device is presented.

Climate sensitivity and parameter coherency in annually resolved δ13C and δ18O from Pinus uncinata tree-ring data in the Spanish Pyrenees

We explore the 20th century climate sensitivity of annually resolved carbon and oxygen isotope ratios in five Pinus uncinata individuals from the upper treeline in ~2400m asl of the Spanish Pyrenees. Time series of δ13C and δ18O are calibrated against temperature, precipitation, and drought indices over the period 1901–2009. Negative correlations of δ13C with summer precipitation and drought indices, as well as positive correlations with summer temperatures, confirm previous evidence from similar habitats in the Pyrenees. In contrast to this summer climate signal in the carbon isotopes, the δ18O record reveals mainly negative correlations with spring precipitation and drought. We explore the coherence between δ13C and δ18O time series derived from individual trees and assess the influence of widely applied δ13C correction procedures on the climate signal strength. Spatial correlation patterns and decomposition of the time series into high- and low-frequency components are used to develop a calibration setup for carbon and oxygen isotope ratios, which will improve long-term climate reconstructions in a region, where classical tree-ring width and density data are limited.

Effect of Calibration Error on Bone Tracking Accuracy With Fluoroscopy

Model-based 3D-fluoroscopy can quantify joint kinematics with 1 mm and 1 deg accuracy level. A calibration based on the acquisition of devices of known geometry is usually applied to size the system. This study aimed at quantifying the sensitivity of the fluoroscopic pose estimation accuracy specifically to errors in the calibration process, excluding other sources of error. X-ray focus calibration error was quantified for different calibration setups, and its propagation to the pose estimation was characterized in-silico. Focus reference position influenced the calibration error dispersion, while calibration cage pose affected its bias. In the worst-case scenario, the estimation error of the principal point and of the focus distance was lower than 1 mm and 2 mm, respectively. The consequent estimation of joint angles was scarcely influenced by calibration errors. A linear trend was highlighted for joint translations, with a sensitivity proportional to the distance between the model and the image plane, resulting in a submillimeter error for realistic calibration errors. The biased component of the error is compensated when computing relative joint kinematics between two segments.

Development of a standing-wave calibration apparatus for acoustic vector sensors

An apparatus was developed to calibrate acoustic hydrophones and vector sensors between 25 and 2000 Hz. A standing-wave field is established inside a vertically oriented, water-filled, elastic-walled waveguide by a piston velocity source at the bottom and a pressure-release boundary condition at the air/water interface. A computer-controlled linear positioning system allows reference hydrophones and/or the device under test to be scanned through the water column while their acoustic response is measured. Some of the challenges of calibrating vector sensors in such an apparatus are discussed, including designing the waveguide to mitigate dispersion, mechanically isolating the apparatus from floor vibrations, understanding the impact of waveguide structural resonances on the acoustic field, and developing processing algorithms to calibrate vector sensors in a standing-wave field. Data from waveguide characterization experiments and calibration measurements will be presented. [Work supported by ARL IR&D.]

Application of Polar Organic Chemical Integrative Sampler (POCIS) to monitor emerging contaminants in tropical waters

Tools specifically validated for tropical environments are needed to accurately describe the behavior of chemical contaminants in tropical ecosystems. In the present study, sampling rates (Rs) were determined for the commercial pharmaceutical-type Polar Organic Chemical Integrative Sampler (POCIS) with a 45.8cm2 exposure surface for 35 Pharmaceutically Active Compounds (PhACs) and Endocrine Disrupting Compounds (EDCs), of which eight compounds (albuterol, atorvastatin, diltiazem, dilantin, enalapril, norfluoxetine, risperidone and warfarin) were reported for the first time. These sampling rates were measured in an outdoor laboratory calibration setup to best capture diurnal tropical temperature variations (29±3°C). The effect of stirring and salinity was investigated. For all compounds, the sampling rates were higher under stirred conditions as compared to quiescent conditions. Calibration results in the presence of 30g sodium chloride support that the effects of salinity on POCIS sampling rates are compound-specific. Comparisons between Time-Weight Average (TWA) water concentrations using POCIS and spot sample levels in the field (2 lake and 1 mangrove estuary sites) are presented. Results showed that POCIS TWA concentrations were in agreement with spot sample concentrations for these aquatic systems. Results indicate that POCIS can be used to effectively measure the TWA concentration for a range of PhACs and EDCs in tropical waters. However, based on the results from mass balance and field deployments, POCIS did not appear suitable for compounds with a low mass balance recovery during calibration (e.g. triclosan and linuron in this study).

CALIBRATING THE NEW ULTRACAM OSPREY OBLIQUE AERIAL SENSOR

Abstract. We present methods and results to calibrate the new oblique sensor UltraCam Osprey which was presented for the first time at the ASPRS 2013 conference and exhibition in Baltimore, MD, March 2013. Even if this was not the first time when oblique sensors were introduced into the market, the UltraCam Osprey did show several new conceptual details which are illustrated in this presentation. The design of the camera is focusing on two important characteristics, a metric nadir component which has been derived from the UltraCam Lp sensor, and collection efficiency through very large swath width. The nadir sensor consists of the 90 megapixel panchromatic camera, true-color RGB, and a near-infrared camera. Adding six oblique camera heads, with two each in forward and backwards direction, results in unmatched oblique collection efficiency. We first explain the camera and cone configuration along with the geometric layout of the sensor system. Then we describe the laboratory setup for geometric calibration of the UltraCam Osprey and the calibration process along with the actual results of one such calibration showing sub-pixel accurate image geometry. This proves that the UltraCam Osprey is a fully calibrated metric camera system suitable for photogrammetric survey applications.

A low-cost stereovision system to estimate size and weight of live sheep

A low-cost dual web-camera high-resolution system was developed to obtain three-dimensional position of homologous points in a scene. Two different softwares have been developed in Matlab environment. The first to acquire couples of frames by the two web-cameras, the second to process the images and obtain the points position in the space and so the distances between points. Distances between points have been corrected using a Partial Least Square regression. The efficiency of the system has been evaluated on a calibration setup experiment and then on 27 live Alpagota sheep. In the calibration phase, at a distance lower than 10m, mean size errors were always lower than 2%. Measures on the Alpagota sheeps showed lower errors for withers height and chest depth (around 3.5%) and higher for body length (around 5.0%). These higher errors, with respect to the ones in the calibration phase, are partially due to the precision of the manual measurements on the animals. Sheep weight estimation using a PLS model on log transformed biometries showed SEP values on the data manually measured and on the stereovision extracted equal to 3.6kg and 4.4kg respectively. Being so inexpensive, ready-to-use and easily transportable this system could find application in other biosystems fields such as forestry, agriculture and environment.

Direct Traceability for Ultra-Pure Water Conductivity

Danish Fundamental Metrology (DFM) has established a calibration setup with direct International System (SI) traceability for conductivity sensors and measurement systems for conductivity of pure t...

Multi-ion transport and reaction model used to improve the understanding of local current density measurements in presence of concentration gradients around a point current source

A departure from the theoretical current density distribution close to a point current source is observed in both Scanning Reference Electrode Technique (SRET) and Scanning Vibrating Electrode Technique (SVET) measurements. Here we report the use of a general multi-ion transport and reaction model, which accounts for micro-convection to point out the origin of the deviations that are experimentally observed. The validity of the model is proven by comparison against both analytical and measured (SRET and SVET) distributions of the current density in a typical calibration setup. Solutions with different conductivities and different impressed currents are considered.

Development of an automatic routine for calibration of thermographic phosphors

An automated routine for the continuous calibration of thermographic phosphors was developed as a replacement for the conventional calibration scheme that relied on fixed temperature points. The automated calibration routine was validated using Mg3F2GeO4:Mn as a calibration phosphor. Hardware and software aspects of the calibration process were addressed in this development. The hardware aspect included a new substrate design using a high performance alloy, the Hastelloy-C alloy, whereas the software aspect included an automated acquisition system which was capable of acquiring simultaneous thermocouple temperatures and phosphor decay waveform in real time. The design of the calibration process eliminates the need for a system in thermal equilibrium during a phosphor calibration measurement. Temperature ramping rates of up to 4 K min−1 were employed in the oven without a delay in the temperature response being measured between the phosphor and the thermocouples involved. In addition, the automated calibration setup allowed for detailed investigations on the effect of heat being delivered to the phosphor coating by the laser. These findings were confirmed by a simple heat transfer model, based on lumped system analysis. In comparison to the data acquisition performed at several fixed points with the conventional calibration scheme, the experiment duration was shortened by a factor of 4 with the overall accuracy improved by 1–2 K.

Calibration system with an indirect photoelectric charger for legislated vehicle number emission measurement counters in the single counting mode

A calibration setup has been established to calibrate or validate UN-ECE Regulation 83 compliant CPCs. A spark discharge generator (GFG 1000) is used to produce carbon particles. For charge conditioning an indirect photoelectric charger is combined with an electrostatic precipitator instead of the very common radioactive bipolar charger. The particle number concentration is determined with a Faraday cup electrometer. Detailed studies have been conducted to validate the calibration setup. The particle size classification was checked by a screen-type diffusion battery. Moreover the effect of multiple charged particles was investigated. Three independent measurements of the counting efficiency as well as the linearity of a typical regulation compliant counter were performed. The calibration setup was also compared with a similar system using a radioactive bipolar charger. The obtained results demonstrate that the counting efficiency can be measured in a particle size range from 13nm to 60nm with a high repeatability. A linearity check at a particle size of 55nm is possible in a concentration range of 1000–10000cm3. The effect of multiple charged particles produced by the indirect photoelectric charger was found to be negligible. Additionally, the difference between a CAST aerosol and a GFG aerosol as a calibration material is discussed.

Two Dimensional Hydrodynamic Modelling of Northern Bay of Bengal Coastal Waters

Mathematical models have advancement to a point where they are considered to be an effective tool for simulating natural phenomena in coastal regions. This paper discusses the development of Bay of Bengal Model (BoBM), updating of the model with the recent bathymetry and shore line of islands and coastline and upgrading from rectangular grid to finer size of mesh grids by using latest version of MIKE21 FM modeling system. This model is very useful for the hydrodynamic study in the coastal region of Bangladesh. The article also presents the model set-up, boundary conditions and few calibration results of the model. The model applications clearly show the variation of the flow structure, their speed and direction separately for monsoon and dry season around the model area which covers the northern part of Bay of Bengal.

In situ Quality Assessment of a Novel Underwater pCO2 Sensor Based on Membrane Equilibration and NDIR Spectrometry

Abstract This paper presents a detailed quality assessment of a novel underwater sensor for the measurement of CO2 partial pressure (pCO2) based on surface water field deployments carried out between 2008 and 2011. The commercially available sensor, which is based on membrane equilibration and nondispersive IR (NDIR) spectrometry is small and can be integrated into mobile platforms. It is calibrated in water against a proven flow-through pCO2 instrument within a custom-built calibration setup. The aspect of highest concern with respect to achievable data quality of the sensor is the compensation for signal drift inevitably connected to absorption measurements. Three means are used to correct for drift effects: (i) a filter correlation or dual-beam setup, (ii) regular zero gas measurements realized automatically within the sensor, and (iii) a zero-based transformation of two sensor calibrations flanking the time of sensor deployment. Three sensors were tested against an underway pCO2 system during two major research cruises, providing an in situ temperature range from 7.4° to 30.1°C and pCO2 values between 289 and 445 μatm. The average difference between sensor and reference pCO2 was found to be −0.6 ±3.0 μatm with an RMSE of 3.7 μatm.

Evaluation of Chip-tool Interface Temperature: Effect of Tool Coating and Cutting Parameters during Turning Hardened AISI 4340 Steel

In the present context of sustainable manufacturing, investigation of cutting temperature during machining is extremely valuable to address metal cutting issues such as dimensional accuracy, surface finish and tool life. In this study, average chip-tool interface temperature was investigated considering the effect of cutting parameters and the type of coating (coated tools), namely, PVD- applied single-layer TiAlN and CVD-applied multi-layer TiCN/Al2O3/TiN during turning of hardened steel. Mathematical model which can predict the average chip-tool interface temperature was developed based on experimental observations which were obtained in the wide range of cutting conditions. A calibration set-up based on tool-work thermocouple principle was developed to correlate the emf (electro motive force) and the interface temperature. R-squared value for the developed model found 0.9693, indicate that the developed model is reliable and could be used effectively for predicting the interface temperature within the domain of the cutting parameters for the given tool and work material pair. Experimental observations indicate that the interface temperature is higher for CVD-coated multi-layer coated tool in comparison to single-layer TiAlN, which get affected mostly by cutting speed followed by feed. However, depth of cut has negligible influence on interface temperature when using both the coated carbide tools.

Development of a 3D human body library based on polygonal mesh surface for whole body counter set-up calibration

A Whole Body Counter (WBC) is a common facility to routinely assess the internal contamination of exposed workers and especially in the case of radiation release accidents. The calibration of the counting device is usually done by using anthropomorphic physical phantoms representing the human body. Due to such a challenge of having representative physical phantoms a virtual calibration has been introduced. The use of computational phantoms and Monte Carlo methods to simulate radiation transport have been demonstrated to be a worthy alternative, not only as a complementary calibration method but also as a powerful tool for the design and optimization of counting geometries. In this study we introduce a methodology for building a 3D human body library that spans variation in both subject shape and size. Open source codes as MakeHuman and Blender software packages have been used for the creation and modelling of 3D humanoid characters based on polygonal mesh surfaces. Also, a home-made software was developed whose main goal is to convert the binary 3D voxel grid into a MCNPX input file. This paper summarizes (1) the development of the MaMP and FeMP - Male and Female Mesh Phantoms, the two first mesh phantoms generated from a series of 3D human bodies library created at SCK-CEN and (2) presents a comparison between the counting efficiency results obtained from the simulations of both mesh phantoms using MCNPX code.

Design and uncertainty assessment of a setup for calibration of microfluidic devices down to 5 nL min−1

This work focuses on the design and characterization of a system for measuring and calibration of liquid micro-flows down to 5 nL min−1. The experimental setup relies on a telecentric imaging system mounted on a high-precision, computer controlled linear stage to track a moving liquid meniscus in a glass capillary. The position of the linear stage can be automatically adjusted to track the motion of the liquid front over distances of up to 15 cm. All fluidic components were placed inside a temperature regulated chamber at 36.0 ± 1.1 °C with a maximum variability ΔT = ± 0.1 °C for time intervals shorter than 1 h. The combined flow-rate uncertainty has been evaluated for measurement times from 15 s to 1 h and nominal flow rates between 5 and 50 nL min−1. At 5 nL min−1, an extended flow-rate uncertainty better that 8.3% can be attained for measurement times equal to or longer than 60 s. The uncertainty approaches asymptotically 5.4% for measurement times longer than 300 s or flow rates higher than 50 nL min−1.

Design of two blackbody sources for millimeter and sub-millimeter wave Fourier transform spectrometry

This paper describes an experimental setup for the spectral calibration of bolometric detectors used in radioastronomy. The system is composed of a Martin–Puplett interferometer with two identical artificial blackbody sources operating in the vacuum mode at 77K and 300K simultaneously. One source is integrated into a liquid nitrogen cryostat, and the other one into a vacuum chamber at room temperature. The sources were designed with a combination of conical with cylindrical geometries thus forming an orthogonal configuration to match the internal optics of the interfermometer. With a simple mathematical model we estimated emissivities of ε~0.995 for each source.