scholarly journals Limiting Uncertainty Relations in Laser-Based Measurements of Position and Velocity Due to Quantum Shot Noise

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 264 ◽  
Author(s):  
Andreas Fischer
Keyword(s):  
Measurement Uncertainty ◽  
Wave Vector ◽  
Shot Noise ◽  
Measurement Techniques ◽  
Time Of Flight ◽  
Wave Number ◽  
Uncertainty Relations ◽  
Position Measurement ◽  
Information Theoretic ◽  
Measurement Systems

With the ongoing progress of optoelectronic components, laser-based measurement systems allow measurements of position as well as displacement, strain and velocity with unbeatable speed and low measurement uncertainty. The performance limit is often studied for a single measurement setup, but a fundamental comparison of different measurement principles with respect to the ultimate limit due to quantum shot noise is rare. For this purpose, the Cramér-Rao bound is described as a universal information theoretic tool to calculate the minimal achievable measurement uncertainty for different measurement techniques, and a review of the respective lower bounds for laser-based measurements of position, displacement, strain and velocity at particles and surfaces is presented. As a result, the calculated Cramér-Rao bounds of different measurement principles have similar forms for each measurand including an indirect proportionality with respect to the number of photons and, in case of the position measurement for instance, the wave number squared. Furthermore, an uncertainty principle between the position uncertainty and the wave vector uncertainty was identified, i.e., the measurement uncertainty is minimized by maximizing the wave vector uncertainty. Additionally, physically complementary measurement approaches such as interferometry and time-of-flight positions measurements as well as time-of-flight and Doppler particle velocity measurements are shown to attain the same fundamental limit. Since most of the laser-based measurements perform similar with respect to the quantum shot noise, the realized measurement systems behave differently only due to the available optoelectronic components for the concrete measurement task.

Miniaturization of an interferometric distance sensor employing diffractive optics

2014 ◽  
Vol 3 (4) ◽  
Author(s):  
Nektarios Koukourakis ◽  
Robert Kuschmierz ◽  
Michael Bohling ◽  
Jürgen Jahns ◽  
Andreas Fischer ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Techniques ◽  
Turbine Blades ◽  
Numerical Aperture ◽  
Optical Element ◽  
Systematic Measurement ◽  
Position Measurement ◽  
Common Path ◽  
The Common ◽  
Path Detection

AbstractIn order to improve safety, lifetime and energy efficiency of turbo machines, the behavior of the turbine blades has to be monitored during operation. This is a great challenge for metrology, since small, robust and non-contact position measurement techniques are required that offer both micrometer accuracy and microsecond temporal resolution. The Laser-Doppler-Distance (LDD) -Sensor proved to be an adequate technique to perform such measurements. However, the usage in turbo machines requires a miniaturized and temperature-stable sensor-head. In this paper we introduce a miniaturized design of the LDD-sensor that is based on common-path detection. First results indicated that the numerical aperture of the common-path detection is small in comparison to former implementations that used separate paths for illumination and detection. We find that decreasing the numerical aperture strongly increases the systematic measurement uncertainty. For this purpose a novel diffractive optical element containing a diffracting-lens was designed and used to increase the numerical aperture of the common-path detection without affecting the sensor size. Experiments prove that the new element reduces the relative systematic measurement uncertainty by a factor of ten. The mean systematic position measurement uncertainty amounts to Δ

Blade Tip Clearance Measurement Systems for High Speed Turbomachinery Applications and the Potential for Blade Tip Timing Applications

2020 ◽  
Author(s):  
Jack David Stubbs ◽  
Muhammad Arslan Shahid
Keyword(s):  
Measurement Uncertainty ◽  
High Speed ◽  
Radial Displacement ◽  
Measurement Techniques ◽  
Test System ◽  
Tip Clearance ◽  
Optical Systems ◽  
Measurement Systems ◽  
Blade Tip ◽  
Blade Tip Clearance

Abstract As turbomachinery OEMs focus efforts to further increase reliability, power and efficiencies, the running clearance between blade tips and stator continue to be of the utmost importance. This paper investigates the capability of capacitive tip clearance systems to perform individual blade tip clearance measurements on high speed rotors of up to 90,000rpm. A rotor was designed using finite element analysis; unique blade responses have been predicted. The objective of this investigation was to consider two different approaches to the application of blade tip clearance measurements and the system requirements to accurately measure low levels of radial displacement of a target rotating between 1,000rpm and 90,000rpm. The first uses the standard approach with passive probes and the second, a new technique using active probes that have demonstrated bandwidths of 1.2MHz and increased measuring range with a lower level of measurement uncertainty. Both systems’ approaches are compared, and their capabilities are evaluated for high-speed applications. The higher bandwidth capabilities of the latter system, combined with smaller sensor diameters, produces comparable signal rise times to the optical systems used in blade tip timing measurements. The difference in approach offers the potential of contamination resistant sensors for long term blade tip timing applications and measurement probes that do not require cooling systems to withstand higher temperature applications. The use of different probe configurations, in a number of applications, has demonstrated a two-fold improvement in the measurement range whilst producing lower levels of noise and uncertainty when applied to blade targets made from composites, aluminium and nickel-alloy materials. The measurement data presented includes individual blade’s radial displacement, identified shaft axial displacement, effects of resonance in the test system and the identification of the main drivers of measurement uncertainty along with an achievable value. The capacitive measurement systems’ performance for blade tip clearance is analysed and reported. The capability to perform other measurement techniques such as blade tip timing with a dual use measurement probe is also analysed and reported. This is done by correlating measurement results between the capacitive systems with that of a repeat measurement of the same target using an optical BTT system.

scholarly journals Gear Shape Measurement Potential of Laser Triangulation and Confocal-Chromatic Distance Sensors

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 937
Author(s):  
Marc Pillarz ◽  
Axel von Freyberg ◽  
Dirk Stöbener ◽  
Andreas Fischer
Keyword(s):  
Measurement Uncertainty ◽  
Surface Properties ◽  
Optical Sensors ◽  
Laser Triangulation ◽  
Shape Measurement ◽  
Full Potential ◽  
Position Measurement ◽  
Standard Measurement ◽  
Measurement Systems ◽  
Measurement Approach

The demand for extensive gear shape measurements with single-digit µm uncertainty is growing. Tactile standard gear tests are precise but limited in speed. Recently, faster optical gear shape measurement systems have been examined. Optical gear shape measurements are challenging due to potential deviation sources such as the tilt angles between the surface normal and the sensor axis, the varying surface curvature, and the surface properties. Currently, the full potential of optical gear shape measurement systems is not known. Therefore, laser triangulation and confocal-chromatic gear shape measurements using a lateral scanning position measurement approach are studied. As a result of tooth flank standard measurements, random effects due to surface properties are identified to primarily dominate the achievable gear shape measurement uncertainty. The standard measurement uncertainty with the studied triangulation sensor amounts to >10 µm, which does not meet the requirements. The standard measurement uncertainty with the confocal-chromatic sensor is <6.5 µm. Furthermore, measurements on a spur gear show that multiple reflections do not influence the measurement uncertainty when measuring with the lateral scanning position measurement approach. Although commercial optical sensors are not designed for optical gear shape measurements, standard uncertainties of <10 µm are achievable for example with the applied confocal-chromatic sensor, which indicates the further potential for optical gear shape measurements.

scholarly journals Comparative Accuracy Analysis of Truck Weight Measurement Techniques

2021 ◽  
Vol 11 (2) ◽  
pp. 745
Author(s):  
Sylwia Stawska ◽  
Jacek Chmielewski ◽  
Magdalena Bacharz ◽  
Kamil Bacharz ◽  
Andrzej Nowak
Keyword(s):  
Measurement Techniques ◽  
Highway Traffic ◽  
Highway Infrastructure ◽  
Measurement Systems ◽  
Motion System ◽  
Weigh In Motion ◽  
Comparative Accuracy ◽  
Bridge Weigh In Motion ◽  
Rational Management ◽  
Truck Weight

Roads and bridges are designed to meet the transportation demands for traffic volume and loading. Knowledge of the actual traffic is needed for a rational management of highway infrastructure. There are various procedures and equipment for measuring truck weight, including static and in weigh-in-motion techniques. This paper aims to compare four systems: portable scale, stationary truck weigh station, pavement weigh-in-motion system (WIM), and bridge weigh-in-motion system (B-WIM). The first two are reliable, but they have limitations as they can measure only a small fraction of the highway traffic. Weigh-in-motion (WIM) measurements allow for a continuous recording of vehicles. The presented study database was obtained at a location that allowed for recording the same traffic using all four measurement systems. For individual vehicles captured on a portable scale, the results were directly compared with the three other systems’ measurements. The conclusion is that all four systems produce the results that are within the required and expected accuracy. The recommendation for an application depends on other constraints such as continuous measurement, installation and operation costs, and traffic obstruction.

UAS measurements for the investigation of emissions of air pollutants at the Duesseldorf airport and industrial sites in the Rhine-Ruhr area, Germany

2021 ◽  
Author(s):  
Konradin Weber ◽  
Christian Fischer ◽  
Martin Lange ◽  
Tobias Pohl ◽  
Tim Kramer ◽  
...  
Keyword(s):  
Data Transmission ◽  
Air Pollutants ◽  
High Reliability ◽  
Measurement Techniques ◽  
Transmission System ◽  
Online Data ◽  
Ruhr Area ◽  
Measurement Systems ◽  
Industrial Sites ◽  
Data Transmission System

&lt;p&gt;Instrumented UAS (unmanned aerial systems, drones) can substantially enhance the capabilities for the investigation of air pollutants, when equipped with the appropriate and customized air pollution measurement systems. Important advantages can be found in the exploration of vertical and horizontal pollutant profiles as well as in the determination of fugitive emissions. The HSD Laboratory for Environmental Measurement Techniques (UMT) has developed a series of different multicopter UAS for various measurement tasks and payloads. Additionally, different commercial UAS are used by UMT. The multicopter UAS are equipped, depending on the measurement task, with different specifically adopted lightweight measurement systems for aerosols (PM10, PM2.5, PM1, UFP, PNC, number size distributions) or gases like O&lt;sub&gt;3&lt;/sub&gt;, SO&lt;sub&gt;2&lt;/sub&gt;, NO&lt;sub&gt;X&lt;/sub&gt;, CO&lt;sub&gt;2&lt;/sub&gt; and VOCs. All measurement systems were intercompared with certified standard measurement equipment before use to assure the quality of the measurement results. Moreover, physical samples of aerosols can be taken during the flight, which enables a chemical or REM analysis after the flight.&lt;/p&gt;&lt;p&gt;Additionally, UMT developed an on-line data transmission system, which allows the transmission of measurement data during the flights from the UAS to the ground for continuous monitoring. In this way concentration plumes can be tracked and hotspots can be pinpointed during the flight. This online data transmission system is independent of commercial platforms, can work on different radio frequencies in a push mode (presently on 2.4 GHz) and communicates with RS232 and I&lt;sup&gt;2&lt;/sup&gt;C interfaces. Within several intercomparison studies this online data transmission proved a high reliability and correctness of transmitted data.&lt;/p&gt;&lt;p&gt;In addition to technical details of the UAS and instrumentation we present in this contribution the results of different measurement campaigns based on our UAS measurements:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Investigations of emissions from the Duesseldorf airport combining upwind and downwind UAS measurements. These investigations became of special interest, as due to the reduced air traffic caused by the Corona pandemia now single aircraft starts and landings could be monitored with their emissions at elevated altitudes.&lt;/li&gt; &lt;li&gt;Investigations of vertical concentration profiles above the city of Duesseldorf, which could be influenced by industrial sites in the north of Duesseldorf as well as by the Duesseldorf airport.&lt;/li&gt; &lt;li&gt;Investigations of vertical and horizontal pollution distributions near, at and around industrial sites in the Rhine Ruhr area, especially of metal industry plants and chemical plants.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;These examples highlight the capabilities of UAS measurements, which will be further enhanced by planned simultaneous use of several UAS in parallel and joint tasks.&lt;/p&gt;

scholarly journals Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

2017 ◽  
Vol 10 (1) ◽  
pp. 247-264 ◽  
Author(s):  
Aditya Choukulkar ◽  
W. Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann Weickmann ◽  
Timothy A. Bonin ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Techniques ◽  
Vertical Plane ◽  
Complex Flow ◽  
Field Campaign ◽  
Velocity Statistics ◽  
Spatial Coverage ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Measurement Uncertainties

Abstract. Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO, from 2 March to 31 May 2015 brought together a large suite of in situ and remote sensing measurement platforms to evaluate complex flow measurement strategies. In this paper, measurement uncertainties for different single and multi-Doppler strategies using simple scan geometries (conical, vertical plane and staring) are investigated. The tradeoffs (such as time–space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single-/multi-Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty. It was found that with an increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity along with horizontal homogeneity and less representative line-of-sight velocity statistics. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.

Total and fractional bedload transport in alpine streams approximated by different surrogate measurement systems

2021 ◽  
Author(s):  
Lorenz Ammann ◽  
Tobias Nicollier ◽  
Alexandre Badoux ◽  
Dieter Rickenmann
Keyword(s):  
Grain Size ◽  
Measurement Techniques ◽  
Bedload Transport ◽  
Accelerometer Sensor ◽  
Protection Measures ◽  
Measurement Systems ◽  
Size Classes ◽  
Alpine Streams ◽  
Surrogate Measurement ◽  
Using Data

&lt;p&gt;Knowledge about bedload transport in rivers is of high importance for many hydraulic engineering applications, in particular related to flood protection measures. Passive acoustic surrogate measurement techniques provide useful continuous estimates of bedload transport in terms of total mass, as well as for different grain-size classes.&lt;/p&gt;&lt;p&gt;We compare different surrogate measurement systems regarding their performance in quantifying total and fractional bedload transport in three alpine streams. The investigated measurement systems are the well-established Swiss plate geophone (SPG), an equivalent system in which the geophone sensor is replaced by an accelerometer sensor, and the miniplate accelerometer (MPA) system. The latter is a more recent device and consists of four small square metal plates embedded in elastomere elements. While the signal recorded with the SPG is known to be proportional to the transported bedload mass, we find that the MPA-signal shows a non-linear dependency. In addition, the MPA reacts more sensitively to small grain size classes than the other two systems, indicating a possible alternative to improve the quantification of bedload transport consisting of those classes.&lt;/p&gt;&lt;p&gt;Based on the raw signal recorded with the SPG and the MPA in a flume experiment, we test the ability of different empirical models to predict the known weight of the impacting particle. We show that it is possible to identify the particle weight with high accuracy with relatively simple models using data of either of the two measurement systems. One remaining challenge is to account for the site-to-site variability in the (amount of) signal caused by the combination of differing numbers of plates in the measurement setup and the lateral transmission of the signal across multiple plates, especially for the SPG system.&lt;/p&gt;

Shear Thickness Modes in a Presence of Magnetoelastic Waves Parallel to a Surface Guided by Ferromagnetic Film

2009 ◽  
Vol 152-153 ◽  
pp. 381-384
Author(s):  
Z.V. Gareeva ◽  
R.A. Doroshenko
Keyword(s):  
Wave Vector ◽  
Ferromagnetic Film ◽  
Wave Number ◽  
Resonant Frequencies ◽  
Surface Plane ◽  
Shear Modes ◽  
Thickness Shear ◽  
Magnetoelastic Waves

Thickness modes of magnetoelastic waves (MEW) guided by ferromagnetic film have been investigated. Propagation of two mutually perpendicular MEW one of which is parallel to a normal to the surface has been considered. It has been shown that resonant frequencies of standing MEW depend on the wave number of a wave propagating along a surface. Plots illustrating dependence of thickness shear modes upon wave vector kz of MEW traveling in a surface plane have been presented.

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