Accurate Power Measurements Research Articles

AC power measurements of electric drives: a method incorporating calorimetry and DC measurements only

Power analyzer specify their power measurement accuracy typically for sinusoidal signals only. In inverter applications, however, signals result from a switching operation and are therefore broadband. This article presents a method for providing a reference result for AC power measurements between inverter and motor. The reference power is determined by a combination of DC measurements and calorimetry and therefore it is independent of the AC signal’s waveform.

Marcher: A Heterogeneous System Supporting Energy-Aware High Performance Computing and Big Data Analytics

Abstract Excessive energy consumption is a major constraint in designing and deploying the next generation of supercomputers. Minimizing energy consumption of high performance computing and big data applications requires novel energy-conscious technologies (both hardware and software) at multiple layers from architecture, system support, and applications. In the past decade, we have witnessed the significant progress toward developing more energy-efficient hardware and facility infrastructure. However, the energy efficiency of software has not been improved much. One obstacle that hinders the exploration of green software technologies is the lack of tools and systems that can provide accurate, fine-grained, and real-time power and energy measurement for technology evaluation and verification. Marcher, a heterogeneous high performance computing infrastructure, is built to fill the gap by providing support to research in energy-aware high performance computing and big data analytics. The Marcher system is equipped with Intel Xeon CPUs, Intel Many Integrated Cores (Xeon Phi), Nvidia GPUs, power-aware memory systems and hybrid storage with Hard Disk Drives (HDDs) and Solid State Disks (SSDs). It provides easy-to-use tools and interfaces for researchers to obtain decomposed and fine-grained power consumption data of these primary computing components. This paper presents the design of the Marcher system and demonstrates the usage of Marcher power measurement tools to obtain detailed power consumption data in various research projects.

Parallel Spectral Acquisition with Orthogonal ICR Cells.

FT-based high performance mass analyzers yield increased resolving power and mass measurement accuracy, yet require increased duration of signal acquisition that can limit many applications. The implementation of stronger magnetic fields, multiple detection electrodes for harmonic signal detection, and an array of multiple mass analyzers arranged along the magnetic field axis have been used to decrease required acquisition time. The results presented here show that multiple ion cyclotron resonance (ICR) mass analyzers can also be implemented orthogonal to the central magnetic field axis. The orthogonal ICR cell system presented here consisting of two cells (master and slave cells) was constructed with printed circuit boards and installed within a single superconducting magnet and vacuum system. A master cell was positioned, as is normally done with ICR cells, on the central magnetic field axis and a slave cell was located off this central axis, but directly adjacent and alongside the master cell. To achieve ion transfer between cells, ions that were initially trapped in the master cell were drifted across the magnetic field into the slave cell with application of a small DC field applied perpendicularly to the magnetic field axis. A subsequent population of ions was injected and accumulated in the master cell. Simultaneous excitation of cyclotron motion of ions in both cells was carried out; ICR signals from each cell were independently amplified and recorded in parallel. Presented here are the initial results of successful parallel spectral acquisition with this orthogonal dual ICR cell array. Graphical Abstract ᅟ.

Formulation of phasor unbalance power: application to sinusoidal power systems

Imbalances significantly reduce the efficiency of electric power systems. There are several negative effects of these phenomena, and they have been extensively studied within the scientific community. The accurate determination and measurement of the unbalance power at any point in a power system aids in the elimination of such type of not useful energies. In this study, a new formulation of the phasors of unbalance power in electric systems is presented. The phasors caused by the unbalance current and unbalance voltage are deduced from the expressions of instantaneous power. From them, the total phasor of unbalance power in the system is proposed. To demonstrate the validity of the proposed formulation, a four-wire system formed by two nodes is used.

A Compact, High Power Capable, and Tunable High Directivity Microstrip Coupler

A coupler is an indispensable component to sample the forward and reflected power for the real-time radio frequency (RF) power monitoring system. The directivity of a coupler is a critical factor to achieve accurate RF power measurements. This paper proposes a microstrip coupler with a tunable high directivity circuit to accurately measure the reflected RF power. The directivity tuner composed of passive components adjusts phase and amplitude of the coupled RF signal, and cancel out the leakage signal from the RF input port at the coupled reflection port. The experimental results, which agree with simulation results, show that the microstrip coupler with the directivity tuner circuit has a compact size (~ 0.07 λg x 0.05 λg), high power capability (up to 1 kW), and high directivities (more than 40 dB) at operating frequency bands (f = 297.3 MHz, 400 MHz, and 447 MHz, respectively) for magnetic resonance imaging (MRI) applications.

The Enigmatic Cornea and Intraocular Lens Calculations: The LXXIII Edward Jackson Memorial Lecture

To review the progress and challenges in obtaining accurate corneal power measurements for intraocular lens (IOL) calculations. Personal perspective, review of literature, case presentations, and personal data. Through literature review findings, case presentations, and data from the author's center, the types of corneal measurement errors that can occur in IOL calculation are categorized and described, along with discussion of future options to improve accuracy. Advances in IOL calculation technology and formulas have greatly increased the accuracy of IOL calculations. Recent reports suggest that over 90% of normal eyes implanted with IOLs may achieve accuracy to within 0.5 diopter (D) of the refractive target. Though errors in estimation of corneal power can cause IOL calculation errors in eyes with normal corneas, greater difficulties in measuring corneal power are encountered in eyes with diseased, scarred, and postsurgical corneas. For these corneas, problematic issues are quantifying anterior corneal power and measuring posterior corneal power and astigmatism. Results in these eyes are improving, but 2 examples illustrate current limitations: (1) spherical accuracy within 0.5 D is achieved in only 70% of eyes with post-refractive surgery corneas, and (2) astigmatism accuracy within 0.5 D is achieved in only 80% of eyes implanted with toric IOLs. Corneal power measurements are a major source of error in IOL calculations. New corneal imaging technology and IOL calculation formulas have improved outcomes and hold the promise of ongoing progress.

Tractor hydraulic power data acquisition system

Tractor hydraulic power is used on a wide range of agricultural implements; however, the availability of operational hydraulic data at points other than full engine throttle position is limited. Operators could utilize this hydraulic data to maximize field efficiency and minimize machinery costs when determining suitable machinery for field operations. A field usable hydraulic test apparatus capable of measuring tractor hydraulic pressure and flow rate data was developed. The goal of this study was to determine if a hydraulic flow and pressure measurement device could be installed on the rear of a tractor to provide implement hydraulic power consumption at different hydraulic hose orientations. The measurement system installed allowed hydraulic lines from the tractor hydraulic remote ports to be attached to the flowmeter and pressure sensors at multiple angles of 0°, 45°, and 90° in different configuration layouts. Tests were performed at different flows and pressures for each hose configuration. The pressures were compared across configurations to a base line reading from a hydraulic pressure and flow rate measurement apparatus used by the Nebraska Tractor Test Laboratory (NTTL). Pressure deviations from the base line were small and ranged between 10.56kPa and 32.2kPa. Flow rate differences (<167mLmin−1) were determined to be negligible (<0.5%). Calculated power differences (<33W) were less than 1% full scale power measured. This small power loss suggested that using the hydraulic measurement apparatus developed as part of this study would enable accurate measurements of tractor hydraulic power provided to implements regardless of hydraulic hose bend angles.

Novel pyroelectric detectors for accurate THz power measurements

Abstract Novel pyroelectric THz detectors have been developed in close cooperation between PTB, the National Metrology Institute of Germany, and the Sensor- und Lasertechnik company. Covering the broad spectral range from below 50 GHz to beyond 5 THz, these detectors are suited to measure the absolute THz power of time-domain spectroscopy (THz-TDS) systems for the first time.

Pilot study on dry eye affecting the accuracy of intraocular lens power measurement in age-related cataract

Background The incidence of dry eye is gradually increasing, and the aging of population is one of factors. Researches showed that the change of tear film stability leads to shift of corneal refractive power, which probably affects the measurement of intraocular lens (IOL) power. The influence of dry eye on the calculation of IOL power is worth paying close attention. Objective This study was to investigate the influence of dry eye on the accuracy of IOL power calculation in age-related cataractous patients. Methods A non-randomized controlled clinical study was performed. Two hundred and sixteen eyes of 216 cataract patients were enrolled in Yanbian Eye Ear Nose and Throat Hospital from May 2013 to February 2014. The visual acuity, intraocular pressure, break up time of tear film (BUT), SchirmerⅠtest (SⅠt) and corneal fluorescein staining were examined in all the eyes, and then the patients were assigned to mild dry eye group (73 eyes), severe dry eye group (68 eyes) and non-dry eye control group (75 eyes). The axial length (AL) and anterior chamber depth (ACD) were measured using IOL Master for the calculation of IOL power and K value (corneal curvature). Phacoemulsification with IOL implantation was performed on all the eyes, and the refractive power was measured with KR 8100 automatic optometry 2 months after operation. The mean absolute refractive error (MARE) between actual refraction and predicted refraction was calculated, and percentage of eyes in different refractive error ranges was compared between the dry eye group and non-dry eye control group. The correlations of dry eye-related parameters with peroperative K value and refractive error were analyzed. This study was approved by the Ethics of Yanbian University, and written informed consent was obtained from each subject prior to entering the cohort. Results No significant differences were found in age, gender, AL, ACD and MARE among the mild dry eye group, severe dry eye group and non-dry eye control group (all at P>0.05), and significant differences in BUT, SⅠt and corneal fluorescein staining scores were found among these three groups (F=5.460, 4.521, 3.572, all at P<0.05). The K values were (43.59±1.39), (44.66±1.53) and (43.42± 1.32)D in the mild dry eye group, severe dry eye group and non-dry eye control group, and the K value in the severe dry eye group was significantly higher than that in the non-dry eye control group (P=0.012). The percentage of eyes with + 0.50-+ 0.75 D deviation was significantly elevated(28.8% versus 13.3%), and that with -0.50--0.75 D deviation was significantly declined (17.3% versus 28.0%)in the dry eye group compared with non-dry eye control group (χ2=4.513, P=0.032; χ2=4.236, P=0.037). A negative correlation was found between BUT and K value (r=-0.204, P=0.011). Conclusions Dry eye affects the accuracy of the determination of IOL power. Compared with the preoperative refraction predictive value, the postoperative refraction shift toward hyperopia. Key words: [Key words] Biometry; Dry eye; Cataract; Refractive error; Intraocular lens power

Multiplying probe for accurate power measurements on an RF driven atmospheric pressure plasma jet applied to the COST reference microplasma jet

In this paper a new multiplying probe for measuring the power dissipated in a miniature capacitively coupled, RF driven, atmospheric pressure plasma jet (μAPPJ—COST Reference Microplasma Jet—COST RMJ) is presented. The approach aims for substantially higher accuracy than provided by traditionally applied methods using bi-directional power meters or commercially available voltage and current probes in conjunction with digitizing oscilloscopes. The probe is placed on a miniature PCB and designed to minimize losses, influence of unknown elements, crosstalk and variations in temperature. The probe is designed to measure powers of the order of magnitude of 0.1–10 W. It is estimated that it measures power with less than 2% deviation from the real value in the tested power range. The design was applied to measure power dissipated in COST-RMJ running in helium with a small addition of oxygen.

Accuracy of Corneal Power Measurements for Intraocular Lens Power Calculation after Myopic Laser In situ Keratomileusis.

Purpose:To evaluate the accuracy of corneal power measurements for intraocular lens (IOL) power calculation after myopic laser in situ keratomileusis (LASIK).Methods:The study evaluated 45 eyes with a history of myopic LASIK. Corneal power was measured using manual keratometry, automated keratometry, optical biometry, and Scheimflug tomography. Different hypothetical IOL power calculation formulas were performed for each case.Results:The steepest mean K value was measured with manual keratometry (37.48 ± 2.86 D) followed by automated keratometry (37.31 ± 2.83 D) then optical biometry (37.06 ± 2.98 D) followed by Scheimflug tomography (36.55 ± 3.08). None of the K values generated by Scheimflug tomography were steeper than the measurements from the other 3 instruments. Using equivalent K reading (EKR) 4 mm with the Double-K SRK/T formula, the refractive outcome generated 97.8% of cases within ± 2 D, 80.0% of cases within ± 1 D, and 42.2% of cases within ± 0.5 D. The best combination of formulas was “Shammas-PL + Double-K SRK/T formula using EKR 4 mm.”Conclusion:Scheimflug tomography imaging using the Holladay EKR 4 mm improved the accuracy of IOL power calculation in post-LASIK eyes. The best option is a combination of formulas. We recommended the use the combined “Shammas-PL ± Double-K SRK/T formula using EKR 4 mm”h for optical outcomes.

High-Speed Peltier Calorimeter for the Calibration of High-Bandwidth Power Measurement Equipment

Accurate power measurements of electronic components operating at high frequencies are vital in determining where power losses occur in a system such as a power converter. Such power measurements must be carried out with equipment that can accurately measure real power at high frequency. We present the design of a high speed calorimeter to address this requirement, capable of reaching a steady state in less than 10 minutes. The system uses Peltier thermoelectric coolers to remove heat generated in a load resistance, and was calibrated against known real power measurements using an artificial neural network. A dead zone controller was used to achieve stable power measurements. The calibration was validated and shown to have an absolute accuracy of +/-8 mW (95% confidence interval) for measurements of real power from 0.1 to 5 W.

Direct Real-Time Power Measurement of a High-Power Electron Cyclotron Maser by a Simple One-Point Schottky Detector Signal

Measurements of the absolute power of high-power millimeter/THz wave generators have been considered to be highly variable and to occasionally produce faulty results owing to experimental difficulty. In this study, we propose a calibration-free method for real-time power measurement of an electron cyclotron maser system, a so-called gyrotron. We demonstrate the feasibility of the method by using a recently developed W-band gyrotron with a peak power of tens of kilowatts. The technique is based on transmitter antenna power measurement by using the Friis transmission equation with a defined gyrotron antenna gain. The new technique will allow extremely simple and accurate real-time measurement of output power over a wide dynamic range ( ${>} {\hbox{50}}$ dB) for continuous wave sources to high-power millimeter/THz wave sources with nanosecond pulse lengths.

Design of a High-Performance Micro Integrated Surface Plasmon Resonance Sensor Based on Silicon-On-Insulator Rib Waveguide Array.

Based on silicon-on-insulator (SOI) rib waveguide with large cross-section, a micro integrated surface plasmon resonance (SPR) biochemical sensor platform is proposed. SPR is excited at the deeply etched facet of the bend waveguide by the guiding mode and a bimetallic configuration is employed. With the advantages of SOI rib waveguide and the silicon microfabrication technology, an array of the SPR sensors can be composed to implement wavelength interrogation of the sensors’ output signal, so the spectrometer or other bulky and expensive equipment are not necessary, which enables the SPR sensor to realize the miniaturization and integration of the entire sensing system. The performances of the SPR sensor element are verified by using the two-dimensional finite-different time-domain method. The parameters of the sensor element and the array are optimized for the achievement of high performance for biochemical sensing application. As a typical example, a single bimetallic SPR sensor with 3 nm Au over 32 nm Al possesses a high sensitivity of 3.968 × 104 nm/RIU, a detection-accuracy of 14.7 μm−1. For a uniparted SPR sensor, it can achieve a detection limit of 5.04 × 10−7 RIU. With the relative power measurement accuracy of 0.01 dB, the refractive index variation of 1.14 × 10−5 RIU can be detected by the SPR sensor array.

Predictability of Sirius dual-scanning corneal tomography in the measurement of corneal power after photorefractive surgery.

Determining an accurate central corneal power (K) measurement is crucial for calculating the intraocular lens power in patients who are undergoing cataract extraction. The ideal method for measuring K is to use a device that works independently of the refractive surgery information. The Scheimpflug camera system offers a promising means of measuring the true corneal power after keratorefractive surgery. In this study, we investigated the accuracy of this system in measuring central corneal power after photorefractive corneal surgery by comparing it to the theoretically derived central corneal power by history method. A total of 120 eyes of 65 (35 females and 30 males) patients were included in this study. The mean change of refraction at the spectacle plane was 3.75 D, whereas the mean change of refraction at the corneal plane was 3.37 D. Using the Sirius dual-scanning corneal tomography, the mean change in corneal power was 3.96 D. No significant differences were detected between the mean post-operative corneal power measured by the Sirius tomographer and the mean change in refraction at the corneal plane calculated clinically (P = 0.076) and the correlation was found to be high (0.913). This study suggests that Sirius dual-scanning corneal tomography offers high predictability when measuring the central 5 mm corneal power in patients who have had myopic corneal photorefractive surgery.

Accuracy of corneal power measurements for intraocular lens power calculation after myopic laser in-situ keratomileusis

Purpose The aim of the study was to evaluate the accuracy of corneal power measurements for intraocular lens (IOL) power calculation after myopic laser in-situ keratomileusis (LASIK). Setting The study was conducted at the Faculty of Medicine, Alexandria University, Egypt. Patients and methods The study was conducted on 45 eyes that had undergone myopic LASIK previously. Corneal power was measured using manual keratometry, automated keratometry, IOLMaster, and Pentacam. Different hypothetical IOL power calculation formulas were used in each case. Results The steepest mean K value with manual keratometry (37.48 ± 2.86 D) followed by automated keratometry (37.31 ± 2.83 D) and the IOLMaster mean K value (37.06 ± 2.98 D) were steeper than any other mean K value measured by Pentacam. Using 4 mm Holladay equivalent K reading (EKR) with the double-K SRK/T formula, the refractive outcome was good, with 97.8% of cases within ± 2 D, 80.0% of cases within ± 1 D, and 42.2% of cases within ± 0.5 D. The best combination of formulas was 'Shammas-PL+double-K SRK/T using EKR 4 mm'. Conclusion Pentacam Scheimpflug imaging using EKR at 4 mm improved the accuracy of IOL power calculation in post-LASIK eyes. The best option is a combination of formulas. It is recommended to use the mean of the combination of 'Shammas-PL+double-K SRK/T with EKR 4 mm'.

Optical Coherence Tomography Accurately Measures Corneal Power Change from Laser Refractive Surgery

To determine the ability of motion-corrected optical coherence tomography (OCT) to measure the corneal refractive power change due to LASIK. Evaluation of a diagnostic test or technology in a cohort. A total of 70 eyes from 37 subjects undergoing LASIK were measured preoperatively. A total of 39 eyes from 22 subjects were measured postoperatively and completed the study. Consecutive patients undergoing LASIK at the Duke Eye Center who consented to participate were imaged with Placido-ring topography, Scheimpflug photography, and OCT on the day of their surgery. Patients were then reimaged with the same imaging systems at the postoperative month 3 visit. Change in preoperative to postoperative corneal refractive power as measured by each of the imaging modalities was compared with the preoperative to postoperative change in manifest refraction (MRx) using the t test with generalized estimating equations. Corneal refractive power change due to LASIK as measured by Placido-ring topography, Scheimpflug photography, and OCT compared with the MRx change vertexed to the corneal plane. The change in MRx should correspond to the change in the corneal refractive power from LASIK and was considered the reference measurement. In 22 individuals (39 eyes) returning after LASIK, we found no significant difference between the clinically measured pre- to post-LASIK change in MRx and both Scheimpflug photography (P = 0.714) and OCT (P = 0.216). In contrast, keratometry values from Placido-ring topography were found to be significantly different from the measured refractive change (P < 0.001). In addition, of the 3 imaging modalities, OCT recorded the smallest mean absolute difference from the reference measurement with the least amount of variability. Motion-corrected OCT more accurately measures the change in corneal refractive power due to laser refractive surgery than other currently available clinical devices. By offering accurate corneal refractive power measurements in normal and surgically modified subjects, OCT offers a compelling alternative to current clinical devices for determining corneal refractive power.

Power Measurement for Resonant Power Converters Applied to Induction Heating Applications

Nowadays, induction heating (IH) technology is dominating the domestic cooking market due to its advantages such as safety, cleanness, and high efficiency. Such high efficiency and high power density implementations are achieved by means of resonant power converters and, consequently, these need to be accurately controlled. This paper proposes a field-programmable gate array-based online power measurement system which allows the control system to perform the proper power control. The proposed power measurement system measures the output power from the digitized output voltage and current through two low-cost 1-bit second-order ΣΔ analog-to-digital converters. The bitstreams have been analyzed and, taking into account the results, several measurement approaches have been proposed and analyzed. Then, a noise sensitivity analysis has been performed in order to verify the proposed measurements methods. The analytical and simulation results have been tested through a resonant power converter applied to domestic IH whose switching frequency varies from 30 to 80 kHz. A statistical analysis of the implemented measurement approaches has been carried out in order to evaluate the system accuracy. Finally, the selected measurement method has been verified for several vessels. As a conclusion, an accurate and cost-effective output power measurement system is obtained, which can be applied to any resonant converter in the frequency operation range.

Accurate stopping power measurements for (0.21–2.68) MeV/u 1H+ and 4He+ ions crossing thin Al foils; extraction of the (I, b) parameters

The stopping powers of thin Al foils for H+ and 4He+ ions have been measured over the energy range E=(206.03–2680.05)keV/amu with an overall relative uncertainty better than 1% using the transmission method. The derived S(E) experimental data are compared to previous ones from the literature, to values derived by the SRIM-2008 code or compiled in the ICRU-49 report, and to the predictions of Sigmund–Schinner binary collision stopping theory. Besides, the S(E) data for H+ ions together with those for He2+ ions reported by Andersen et al. (1977) have been analyzed over the energy interval E>1.0MeV using the modified Bethe–Bloch stopping theory. The following sets of values have been inferred for the mean excitation potential, I, and the Barkas–Andersen parameter, b, for H+ and He+ projectiles, respectively: (I=164±3)eV, b=1.40 and (I=163±2.5)eV, b=1.38. As expected, the I parameter is found to be independent of the projectile electronic structure presumably indicating that the contribution of charge exchange effects becomes negligible as the projectile velocity increases. Therefore, the I parameter must be determined from precise stopping power measurements performed at high projectile energies where the Bethe stopping theory is fully valid.

New experimental methodology, setup and LabView program for accurate absolute thermoelectric power and electrical resistivity measurements between 25 and 1600 K: application to pure copper, platinum, tungsten, and nickel at very high temperatures.

In this paper we describe an experimental setup designed to measure simultaneously and very accurately the resistivity and the absolute thermoelectric power, also called absolute thermopower or absolute Seebeck coefficient, of solid and liquid conductors/semiconductors over a wide range of temperatures (room temperature to 1600 K in present work). A careful analysis of the existing experimental data allowed us to extend the absolute thermoelectric power scale of platinum to the range 0-1800 K with two new polynomial expressions. The experimental device is controlled by a LabView program. A detailed description of the accurate dynamic measurement methodology is given in this paper. We measure the absolute thermoelectric power and the electrical resistivity and deduce with a good accuracy the thermal conductivity using the relations between the three electronic transport coefficients, going beyond the classical Wiedemann-Franz law. We use this experimental setup and methodology to give new very accurate results for pure copper, platinum, and nickel especially at very high temperatures. But resistivity and absolute thermopower measurement can be more than an objective in itself. Resistivity characterizes the bulk of a material while absolute thermoelectric power characterizes the material at the point where the electrical contact is established with a couple of metallic elements (forming a thermocouple). In a forthcoming paper we will show that the measurement of resistivity and absolute thermoelectric power characterizes advantageously the (change of) phase, probably as well as DSC (if not better), since the change of phases can be easily followed during several hours/days at constant temperature.