Angular Calibration Research Articles

Assessment of Unsteady Pressure Measurement Uncertainty—Part I: Single Sensor Probe

With the advancements in miniaturization and temperature capabilities of piezoresistive pressure sensors, pneumatic probes—which are the long established standard for flow-path pressure measurements in gas turbine environments—are being replaced with unsteady pressure probes. Any measured quantity is by definition inherently different from the “true” value, requiring the estimation of the associated errors for determining the validity of the results and establishing respective confidence intervals. In the context of pressure measurements, the calibration uncertainty values, which differ from measurement uncertainties, are typically provided. Even then, the lack of a standard methodology is evident as uncertainties are often reported without appropriate confidence intervals. Moreover, no time-resolved measurement uncertainty analysis has come to the attention of the authors. The objective of this paper is to present a standard method for the estimation of the uncertainties related to measurements performed using single sensor unsteady pressure probes, with the help of measurements obtained in a one and a half stage low pressure (LP) high speed axial compressor test rig as an example. The methodology presented is also valid for similar applications involving the use of steady or unsteady sensors and instruments. The static calibration uncertainty, steady measurement uncertainties, and unsteady measurement uncertainties based on phase-locked average (PLA) and ensemble average are presented in this contribution. Depending on the number of points used for the averaging, different values for uncertainty have been observed, underlining the importance of having greater number of samples. For unsteady flows, higher uncertainties have been observed at regions of higher unsteadiness such as tip leakage vortices, hub corner vortices, and blade wakes. Unfortunately, the state of the art in single sensor miniature unsteady pressure probes is comparable to multihole pneumatic probes in size, preventing the use of multihole unsteady probes in turbomachinery environments. However, the angular calibration properties of a single sensor probe obtained via an aerodynamic calibration may further be exploited as if a three-hole directional probe is employed, yielding corrected total pressure, unsteady yaw angle, static pressure, and Mach number distributions based on the PLAs with the expense of losing the time-correlation between the virtual ports. The aerodynamic calibration and derivation process are presented together with the assessment of the uncertainties associated to these derived quantities by the authors in Dell'Era et al. (2016, “Assessment of Unsteady Pressure Measurement Uncertainty—Part II: Virtual Three Hole Probe,” ASME J. Eng. Gas Turbines Power, 138(4), p. 041602). In the virtual three-hole mode, similar to that of a single sensor probe, higher uncertainty values are observed at regions of higher unsteadiness.

Mythen detector for X-ray diffraction at the Beijing synchrotron radiation facility

ABSTRACTTime-resolved X-ray powder diffraction may be used to elucidate the structure of polycrystalline matter, but a fast-response full-profile detector is often necessary. This article describes a Mythen detector incorporated in beamline 4B9A of the Beijing Synchrotron Radiation Facility. Basic parameters of this detector are reported, and flat-field correction, angular calibration, eccentric error, and other data treatment for this detector are discussed. X-ray diffraction measurement of lanthanum boride demonstrates that this detector provides high-quality, time-resolved X-ray powder diffraction measurements.

An NN-based SRD decomposition algorithm and its application in nonlinear compensation.

In this study, a neural network-based square root of descending (SRD) order decomposition algorithm for compensating for nonlinear data generated by sensors is presented. The study aims at exploring the optimized decomposition of data 1.00,0.00,0.00 and minimizing the computational complexity and memory space of the training process. A linear decomposition algorithm, which automatically finds the optimal decomposition of N subparts and reduces the training time to and memory cost to , has been implemented on nonlinear data obtained from an encoder. Particular focus is given to the theoretical access of estimating the numbers of hidden nodes and the precision of varying the decomposition method. Numerical experiments are designed to evaluate the effect of this algorithm. Moreover, a designed device for angular sensor calibration is presented. We conduct an experiment that samples the data of an encoder and compensates for the nonlinearity of the encoder to testify this novel algorithm.

Interplay effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc quality assurance.

The purpose of this study is to investigate an effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc QA for 6, 8, 10, and 15 MV The angular dependence was investigated by comparing MapCHECK 2 measurements in MapPHAN‐MC2 to the corresponding Eclipse calculations every 10° using 10 × 10 cm2 and 3 × 3 cm2 fields. Fourteen patients were selected to make RapidArc plans using the four energies, and verification plans were delivered to two phantom setups: MapCHECK 2/MapPHAN phantom (MapPHAN QA) and MapCHECK 2 on an isocentric mounting fixture (IMF QA). Migration of MapCHECK 2 on IMF was simulated by splitting arcs every 10° and displacing an isocenter of each partial arc in the Eclipse system (IMFACTUAL QA). To investigate the effect of calibration field size, MapCHECK 2 was calibrated by two field sizes (10 × 10 cm2 and 3 × 3 cm2) and applied to all QA measurements. The γ test was implemented using criteria of 1%/1 mm, 2%/2 mm, and 3%/3 mm. A mean dose of all compared points for each plan was compared with respect to a mean effective field size of the RapidArc plan. The angular dependence was considerably high at gantry angles of 90° ± 10° and 270° ± 10° (for 10 × 10/3 × 3 cm2 at 90°, 30.6% ± 6.6%/33.4%± 5.8% (6 MV), 17.3% ± 5.3%/15.0% ± 6.8% (8 MV), 8.9% ± 2.9%/7.8% ± 3.2% (10 MV), and 2.2% ± 2.3%/‐1.3% ± 2.6% (15 MV)). For 6 MV, the angular dependence significantly deteriorated the γ passing rate for plans of large field size in MapPHAN QA (< 90% using 3%/3 mm); however, these plans passed the γ test in IMFACTUAL QA (> 95%). The different calibration field sizes did not make any significant dose difference for both MapPHAN QA and IMFACTUAL QA. For 8, 10, and 15 MV, the angular dependence does not make any clinically meaningful impact on MapPHAN QA. Both MapPHAN QA and IMFACTUAL QA presented clinically acceptable γ passing rates using 3%/3 mm. MapPHAN QA showed better passing rates than IMFACTUAL QA for the tighter criteria. The 10 × 10 cm2 calibration showed better agreement for plans of small effective field size (< 5 × 5 cm2) in MapPHAN QA. There was no statistical difference between IMF QA and IMFACTUAL QA. In conclusion, MapPHAN QA is not recommended for plans of large field size, especially for 6 MV, and MapCHECK 2 should be calibrated using a field size similar to a mean effective field size of a RapidArc plan for better agreement for IMF QA.PACS numbers: 87.55.km, 87.55.Qr, 87.56.Fc

Calibration System for Angular Vibration Using Precision Rotary Encoder

본 논문은 고정밀 회전엔코더를 이용한 회전진동 교정시스템의 실현방안을 제안한다. 제안된 시스템과 비교를 위해 한국표준과학연구원의 회전진동 절대교정시스템을 소개하며 회전진동 센서의 교정을 위한 장치와 측정 불확도 모델을 각각 제시한다. 제안된 방법은 회전엔코더의 교정방법에 따라 두 가지 로 나뉘는데 첫 번째는 레이저 간섭계를 이용하여 교정된 엔코더를 사용하는 방법이고, 두 번째는 제조사가 제공하는 성적서를 이용하여 교정 불확도를 평가하는 방법이다. 0.4 ~ 200 Hz의 교정주파수 구간에서 각가속도계를 교정한 결과, 첫 번째 제안된 방법은 절대교정시스템을 기준으로 감도 차이가 0.1 % 그리고 위상 차이는 <TEX>$0.01^{\circ}$</TEX>이내였으며 최대 확장불확도 진폭은 0.6 % 그리고 위상은 <TEX>$0.4^{\circ}$</TEX> 이었다. 두 번째 제안된 방법은 절대교정시스템을 기준으로 감도차이가 진폭은 0.1 % 그리고 위상차이는 <TEX>$0.6^{\circ}$</TEX> 이내였으며 최대 확장불확도는 진폭 4.8 % 와 위상 <TEX>$2.8^{\circ}$</TEX>이었다. In this paper, two calibration methods for angular vibration pickups using a precision rotary encoder are proposed. The KRISS (Korea Research Institute of Standards and Science) primary angular vibration calibration system and the calibration procedures are briefly explained. The rotary encoder is shown to be calibrated in two methods: The one is to use the laser interferometer to calibrate the rotary encoder under test and the other is to exploit the certificate of the encoder supplied. Complex sensitivities measured from the first are shown to be less than 0.1 % difference in magnitude and <TEX>$0.01^{\circ}$</TEX> difference in phase shift in reference to those of the primary calibration system. Their expanded uncertainties were observed to be less than 0.6 % in magnitude and <TEX>$0.4^{\circ}$</TEX> in phase shift over the range of 0.4 to 200 Hz. Under the same calibration conditions, complex sensitivities evaluated by the second method are shown be 0.1 % difference in magnitude and <TEX>$0.6^{\circ}$</TEX> difference in phase shift in reference to those of the primary calibration system. Their expanded uncertainties were seen to be less than 4.8 % in magnitude and <TEX>$2.8^{\circ}$</TEX> in phase shift.

Bilateral comparison CCAUV.V-S1: Primary angular vibration calibration

A comparison CCAUV.V-S1 was organized to compare measurements of sinusoidal angular accelerations in the frequency range from 0.4 Hz to 1 kHz. This was a bilateral comparison between the Korea Research Institute of Standards and Science (KRISS), Republic of Korea, and the Physikalisch-Technische Bundesanstalt (PTB), Germany.Both NMIs applied laser interferometry in compliance with ISO 16063-15:2006 'Methods for the calibration of vibration and shock transducers—Part 15: Primary angular vibration calibration by laser interferometry'.The complex voltage sensitivity (magnitude and phase) of one angular transfer standard in the frequency range of 0.4 Hz to 100 Hz and the complex charge sensitivity (magnitude and phase) of one angular reference standard in the frequency range of 1 Hz to 1000 Hz were measured.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Incorporating variability in honey bee waggle dance decoding improves the mapping of communicated resource locations

Honey bees communicate to nestmates locations of resources, including food, water, tree resin and nest sites, by making waggle dances. Dances are composed of repeated waggle runs, which encode the distance and direction vector from the hive or swarm to the resource. Distance is encoded in the duration of the waggle run, and direction is encoded in the angle of the dancer's body relative to vertical. Glass-walled observation hives enable researchers to observe or video, and decode waggle runs. However, variation in these signals makes it impossible to determine exact locations advertised. We present a Bayesian duration to distance calibration curve using Markov Chain Monte Carlo simulations that allows us to quantify how accurately distance to a food resource can be predicted from waggle run durations within a single dance. An angular calibration shows that angular precision does not change over distance, resulting in spatial scatter proportional to distance. We demonstrate how to combine distance and direction to produce a spatial probability distribution of the resource location advertised by the dance. Finally, we show how to map honey bee foraging and discuss how our approach can be integrated with Geographic Information Systems to better understand honey bee foraging ecology.

A Novel Angular Acceleration Sensor Based on the Electromagnetic Induction Principle and Investigation of Its Calibration Tests

An angular acceleration sensor can be used for the dynamic analysis of human and joint motions. In this paper, an angular acceleration sensor with novel structure based on the principle of electromagnetic induction is designed. The method involves the construction of a constant magnetic field by the excitation windings of sensor, and the cup-shaped rotor that cut the magnetic field. The output windings of the sensor generate an electromotive force, which is directly proportional to the angular acceleration through the electromagnetic coupling when the rotor has rotational angular acceleration. The mechanical structure and the magnetic working circuit of the sensor are described. The output properties and the mathematical model including the transfer function and state-space model of the sensor are established. The asymptotical stability of the sensor when it is working is verified by the Lyapunov Theorem. An angular acceleration calibration device based on the torsional pendulum principle is designed. The method involves the coaxial connection of the angular acceleration sensor, torsion pendulum and a high-precision angle sensor, and then an initial external force is applied to the torsion pendulum to produce a periodic damping angle oscillation. The angular acceleration sensor and the angle sensor will generate two corresponding electrical signals. The sensitivity coefficient of the angular acceleration sensor can be obtained after processing these two-channel signals. The experiment results show that the sensitivity coefficient of the sensor is about 17.29 mv/Krad·s2. Finally, the errors existing in the practical applications of the sensor are discussed and the corresponding improvement measures are proposed to provide effective technical support for the practical promotion of the novel sensor.

The Estimation of Angular Misalignments for Ultra Short Baseline Navigation Systems. Part I: Numerical Simulations

Ultra Short Baseline (USBL) navigation systems are often faced with positioning errors arising from misalignments between sensors. This paper proposes a line survey method for USBL angular alignment calibration. In the scheme of USBL line survey, mathematical representations of positioning error arising from heading, pitch and roll misalignments are derived, respectively. The effect of each misalignment angle and how the differences can be used to calibrate each misalignment angle in turn are presented. An iterative algorithm that takes advantage of the geometry of position errors resulting from angular misalignments is developed for USBL calibration. Numerical simulations are provided to demonstrate the effectiveness of the USBL line survey approach. In addition, the effect of measurement error on the estimation of roll alignment error is evaluated and discussed.

INVESTIGATIONS INTO THE ACCURACY OF ANGLE CALIBRATION

Technical possibilities to create equipment for the calibration of flat angles are discussed in the article. The angular standard measure, the radian, has not been realised as a standard unit until now. Nevertheless, the unit of angular measure in degrees is used as the geometric measure of length in geodesy, machine engineering and other branches of industry – by multiangular prisms – polygons with an autocollimator, rotary tables, circular scales, etc. It should be noted that these angle measures are calibrated against the upper level measures (etalons) only at the several intervals depending on the number of sides (angles) of the polygon or the other standard measure. The methods of calibration of constant angle value in full circle are used as well. At the same time geodetic instruments, rotary tables of metal cutting tools and instruments, rotary encoders have a great number of discrete values. These values between the calibrated points remain unknown during calibration. The information received during calibration relative to all the information available can be evaluated using information entropy. The equipment of calibration permitting to select significantly more information would be essential for better accuracy assurance of instruments used in machine engineering, geodesy, building structures. Theoretical and technical background for justifying and developing such equipment for angular accuracy calibration is presented here. A modern scientific and technical background validates this concept.

Determination of the volume scattering function of aqueous particle suspensions with a laboratory multi-angle light scattering instrument

We describe a methodology for determining the volume scattering function β(ψ) of aqueous particle suspensions from measurements with a laboratory multi-angle light scattering instrument called DAWN (Wyatt Technology Corporation). In addition to absolute and angular calibration, the key component of the method is the algorithm correcting for reflection errors that reduce the percent error in β(ψ) from as much as ~300% to <13% at backward scattering angles. The method is optimized and tested with simulations of three-dimensional radiative transfer of exact measurement geometry including the key components of the instrument and also validated experimentally using aqueous suspensions of polystyrene beads. Example applications of the method to samples of oceanic waters and comparisons of these measurements with results obtained with other light scattering instruments are presented.

Absolute angular calibration of a submarine km 3 neutrino telescope

A requirement for neutrino telescope is the ability to resolve point sources of neutrinos. In order to understand its resolving power a way to perform absolute angular calibration with muons is required. Muons produced by cosmic rays in the atmosphere offer an abundant calibration source. By covering a surface vessel with 200 modules of 5 m 2 plastic scintillator a surface air shower array can be set up. Running this array in coincidence with a deep-sea km 3 size neutrino detector, where the coincidence is defined by the absolute clock timing stamp for each event, would allow absolute angular calibration to be performed. Monte Carlo results simulating the absolute angular calibration of the km 3 size neutrino detector will be presented. Future work and direction will be discussed.

A New Automatic System for Angular Measurement and Calibration in Radiometric Instruments

This paper puts forward the design, construction and testing of a new automatic system for angular-response measurement and calibration in radiometric instruments. Its main characteristics include precision, speed, resolution, noise immunity, easy programming and operation. The developed system calculates the cosine error of the radiometer under test by means of a virtual instrument, from the measures it takes and through a mathematical procedure, thus allowing correcting the radiometer with the aim of preventing cosine error in its measurements.

Optical Angular Encoder Installation Error Measurement and Calibration by Ring Laser Gyroscope

This paper deals with the installation errors of an optical angular encoder (OAE). A harmonic model is proposed to describe the installation errors, including the effects of eccentricity, swash, and distortion. Moreover, a method of OAE calibration with the ring laser gyroscope (RLG) is introduced. The calibration method can potentially reach the accuracy of 0.1. The calibration method is proved to be experimentally effective. With the harmonic model obtained from the experiment, the calibration of the OAE can be carried out in real time.

CONEX, a program for angular calibration and averaging of two-dimensional powder scattering patterns

CONEXis a Windows application for converting series of two-dimensional X-ray powder patterns measured on flat two-dimensional detectors into one-dimensional scattering patterns. It is based on the rigorous use of scattering patterns of calibration samples to determine the three-dimensional position of the detector, with respect to the sample and to the beam. This enables correction of the data for geometric distortions, even when the detector is highly tilted and not centred on the beam.

Angular calibration in energy dispersive X-Ray diffraction by using genetic algorithms

Angular calibration in energy dispersive X-Ray diffraction by using genetic algorithms

Angular calibration in energy dispersive X-Ray diffraction by using genetic algorithms

In Energy Dispersive X-Ray diffraction measurements, the estimate of momentum transfer q, on which the diffracted intensity depends, should be as accurate as possible. Since q, in turn, depends on both the energy and the scattering angle, an error on the latter due to an incorrect positioning of the sample, to the asymmetric angular spread induced by the collimation slits or, in general, to any uncertainty on the geometric setup, results in an uncertainty on the q value. Here, a new self calibration method to correct such errors, based on a genetic algorithm is presented. It is robust, fast and completely automatic. Results obtained by carrying out Energy Dispersive X-Ray Diffraction measurements on reference samples are reported and discussed. They show how the application of such genetic algorithm may provide a fast esteem of the two parameters required when multiple angle pattern collection is performed, namely the effective starting angle and the angular step. In this way, reliable q-values of all the diffraction pattern features (Bragg peaks for crystalline, and diffused bumps for non-crystalline samples) are obtained.

Is an angular standard necessary for rotary encoders?

A rotary encoder is an angular readout that reads an optical pattern written on the circumference of a shaft similar to a 360 degrees protractor and outputs angle position information. Since the output of a rotary encoder deviates from the true angle position due to optical pattern errors or eccentricity of the shaft about the rotation axis, users have encountered difficulty in ensuring the reliability of the angle information derived from an encoder. In order to solve this problem, SelfA: A Self-calibratable Angle device was developed. The SelfA can detect a variety of angle deviation sources by itself, and has the ability to output an angular calibration value. This SelfA can detect the angle deviation value from an optical encoder which has been a black box until now and enables visualization of these factors quantitatively.

Calibration and Validation of an All-Sky Imager

AbstractThe automatic all—sky imager developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences, provides all—sky visible images in the red, green, and blue channels. This paper presents three major calibration experiments of the all—sky imager, geometric angular calibration, optical calibration, and radiometric calibration, and then infers an algorithm to retrieve relative radiance from the all—sky images. Field experiments show that the related coefficient between retrieved radiance and measured radiance is about 0.91. It is feasible to use the algorithm to retrieve radiance from images. The paper sets up a relationship between radiance and the image, which is useful for using the all—sky image in numerical-simulations that predict more meteorological parameters.

SU‐DD‐A2‐05: Uncertanity of Real Time in Vivo Dosimetry with MOSFET Linear Array in I‐125 Prostate Permanent Implant Brachytherapy

Real‐time dose monitoring is important to improve the accuracy of prostate permanent implant brachytherapy (PI). However, few data about in vivo dosimetry in PI have been reported because dosimetry of low energy photons from I‐125 sources is challenging. The purpose of this study is to estimate the dosimetric uncertainty in I‐125 permanent implant brachytherapy using 5‐linear array MOSFET. We evaluated the physical characteristics including angular response variability, linearity, calibration factor, and detector response variability for photon beams from I‐125 seed. All experiments were performed using I‐125 seeds to eliminate the energy dependence. Furthermore phantom study was performed to estimate the dosimetric uncertainty in preclinical settings. For isotropic analysis, the response of 270 and 90 degrees were 8 to 15 % lower than 0 degree and in another angle, the differences of responses were within 5%. However, the deviation of each angle was within 6%. The linearity of the readings is excellent (R2=0.098). The fading effect of MOSFET was not observed. Calibration factor was obtained with the standard deviation within 4%. We found that calibration factor was changed by seed‐detector distance (SDD) by 10% in shorter distance (5mm and 7mm) and 4% in greater distance compared with SDD 10mm. The same tendency was observed by Monte Carlo Simulation. Monte Carlo simulation showed that the beam hardening effect occurred as the SDD increased, which can increase additional deviation. In phantom study, treatment planning was performed with 47 seeds in a modified peripheral loading manner. We measured the urethral dose at base, midland, and apex positions during 20 minutes. In mid grand and base regions, measure dose agreed within 6% and in apex region less than 15% differences were observed. These data suggest that in vivo dosimetry in permanent implant brachytherapy with the appropriate correction can be performed within 15%.