Application of Statistical Tools to Optimize a Dual Source Electrical High Dc Resistance Bridge

At the Istituto Nazionale di Ricerca Metrologica (INRIM), a commercial dual source high resistance bridge has been optimized by means of the application of statistical tools and of the analysis of measurements distributions. These tools help to achieve the best precision for resistance ratio measurements in the range 10 T & OHM; & DIVIDE; 100 T & OHM;. A measurement procedure consisting of multiple steps, in which at each one the value of the resistor under calibration is updated and has been considered the best one. With this procedure, at the third step, the lowest standard deviation of the mean and the measurements distribution approximately normal are obtained regardless of the settle time, of the resistance ratio, of the measurement voltages and of the resistors under comparison. This comes from the achievement of the white noise regime and from a bridge balance close to the ideal. This measurement procedure therefore allows also to achieve the lowest measurement uncertainty due to the minimization of the type A uncertainty. The Allan variance and the power spectral density were used to identify the white noise analyzing the detector readings. Strict triangulation rules were also established and applied to validate both the measurement process and the chosen model to extrapolate the values of the standard resistors at low voltages

Statistical tools for analysis of the performance of a high resistance measurement bridge

Il rapporto tecnico descrive l’utilizzo delle varianze di Allan e della densità di potenza spettrale per individuare le sorgenti di rumore che si possono riscontrare nel funzionamento del ponte di Wheatstone modificato di alta resistenza di tipo commerciale. Lo studio è stato condotto osservando le misure di corrente del detector del ponte in funzione del tempo di integrazione del medesimo. Da un’analisi preliminare dei dati ottenuti sono stati individuate le principali sorgenti di rumore del sistema in corrispondenza dei tempi di integrazione del detectorThe technical report exploits the use of Allan variances and the spectral power density to analyze the performance of the high resistance measurement Wheatstone modified bridge of commercial type. The study was performed by observing the current measurements of the bridge detector as a function of its integration time. From a preliminary analysis of the data obtained, the main sources of noise of the system have been identified in correspondence with the integration times of the detector

Low–frequency noise analyses in measurements of high standard resistance bridges

Presso l'Istituto Nazionale di Ricerca Metrologica (INRiM) è stata effettuata una prima valutazione esplorativa di un modello per il rumore a bassa frequenza delle misure con alti valori di resistenza resistori per un ponte commerciale a doppia sorgente e i valori inferiore e superiore per le regole di triangolazione metrologica restrittive. Lo studio è stato condotto osservando le misure di rapporto di resistenze campione nel campo da 10 Tohm a 1 Pohm, per il calcolo dell’incertezza tipo A. Keywords: Misure di resistori campioni di alto valore, modello equivalente di rapporto di resistenze, incertezza di misura, test di compatibilità, misure affette da rumore, ISO 17025 e la valutazione del rischio.At the National Institute of Metrological Research (INRiM), the first evaluation of an exploratory model in the low-frequency noise in measurements of high-standard resistance commercial bridges and the low limits and high limits has been made using restrictive metrological triangulation rules. The study was performed by observing the ratio measurements of a commercial bridge for the standard resistors in the range from 10 Tohm to 1 Pohm to calculate the type A uncertainty. Keywords: High resistance measurements, equivalent ratio model, measurement uncertainty, self-calibration process, measurement noise, ISO 17025 and the risk assessment

Metrological triangulation rules in ratio measurements of high standard resistance bridges

At the National Institute of Metrological Research (INRiM) a first evaluation for systematic errors of a commercial dual source high resistance bridge has been made using restrictive metrological triangulation rules. This technical report exploits the use of the Allan variance and the spectral power density to achieve optimum performances and its limits in case of the high resistance measurement modified Wheatstone bridge of commercial type. The study was performed observing the ratios measurements of the bridge for the standard resistors in the range from 10 Tohm to 1 Pohm.Presso l'Istituto Nazionale di Ricerca Metrologica (INRiM) è stata effettuata una prima valutazione degli errori sistematici per un ponte commerciale ad alta resistenza a doppia sorgente utilizzando regole di triangolazione metrologica restrittive. Questa relazione tecnica sfrutta l'uso della varianza di Allan e della densità di potenza spettrale per ottenere i limiti di queste regole nel caso del ponte di Wheatstone modificato di tipo commerciale. Lo studio è stato condotto osservando le misure di rapporto di resistenze campione nel campo da 10 Tohm a 1 Pohm.At the National Institute of Metrological Research (INRiM) a first evaluation for systematic errors of a commercial dual source high resistance bridge has been made using restrictive metrological triangulation rules. This technical report exploits the use of the Allan variance and the spectral power density to achieve optimum performances and its limits in case of the high resistance measurement modified Wheatstone bridge of commercial type. The study was performed observing the ratios measurements of the bridge for the standard resistors in the range from 10 Tohm to 1 Pohm

Online Estimation of ARW Coefficient of Fiber Optic Gyro

As a standard method for noise analysis of fiber optic gyro (FOG), Allan variance has too large offline computational burden and data storages to be applied to online estimation. To overcome the barriers, the state space model is firstly established for FOG. Then the Sage-husa adaptive Kalman filter (SHAKF) is introduced in this field. Through recursive calculation of measurement noise covariance matrix, SHAKF can avoid the storage of large amounts of history data. However, the precision and stability of this method are still the primary matters that needed to be addressed. Based on this point, a new online method for estimation of the coefficient of angular random walk is proposed. In the method, estimator of measurement noise is constructed by the recursive form of Allan variance at the shortest sampling time. Then the estimator is embedded into the SHAKF framework resulting in a new adaptive filter. The estimations of measurement noise variance and Kalman filter are independent of each other in this method. Therefore, it can address the problem of filtering divergence and precision degrading effectively. Test results of both digital simulation and experimental data of FOG verify the validity and feasibility of the proposed method

Mõõtemääramatuse hindamine Eesti massi riigietaloni laboratooriumis

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Riigi mõõteinfrastruktuuri tase ja sujuv toimimine on riigi konkurentsivõime, teaduslik-tehnoloogilise suutlikkuse ja elukeskkonna turvalisuse väga oluline element. Alates 2001.a on Eestis Metroloogia keskasutuses Metrosert sisse seatud massi, pikkuse, temperatuuri ja elektriliste suuruste riigietalonid rahvusvahelisel sekundaartasemel. Reeglina kehastab mõõteetalon riigi tipptaset vastavas teaduslik-tehnilises valdkonnas, kuid selle võimalusi saab täielikult ära kasutada vaid siis, kui on kindlustatud etaloni ja nende abil osutatud mõõtetenuste mõõtemääramatuse usaldusväärne hindamine ja rahvusvaheline ekvivalentsus. Etalonide tase ja rahvusvaheline ekvivalentsus ilmneb rahvusvahelise koostöös, eelkõige hea kooskõla kaudu võrdlusmõõtmistel, kusjuures võtmeks tulemuste kooskõla hindamisel on mõõtemäätamatus. Eesti massi riigietaloni laboratoorium realiseerib ja esitab massiskaala piirkonnas 1 mg kuni 50 kg, on võimeline kalibreerima rahvusvahelise klassifikatsiooni järgi kõige täpsemate OIML E1 klassi vihtide massi ja leppelist massi. Võimalik on määrata vihtide magnetiliste omaduste vastavust täpsusklassi nõuetele ja piirkonnas 1 g kuni 2 kg kalibreerida vihtide tihedust. Laboratooriumi käsutuses on kolm automaatset massikomparaatorit, rohkem kui sada vihti ja mitmeid abimõõtevahendeid. Laboratoorium asub konditsioneeritud filtreeritud õhuga mõõteruumis, milles kontrollitakse õhu temperatuuri ja suhtelist niiskust. Mõõtmised põhinevad neljale kogu mõõtepiirkonna ulatuses hoolikalt kontrollitud mõõtemudelile. Mõõtemääramatuse hindamist hõlbustab kõigile olulistele mõõtevahenditele viieteist aasta jooksul kogunenud ulatuslik kalibreerimisajalugu. Lisaks on läbi viidud mitu spetsiaalset uurimust, mis lubavad hinnata mõõtemääramatust paremini kui rutiintöös saadavad üsna napid andmed. Mõõtemääramatuse hindamise aluseks massi riigietaloni laboratooriumis on rahvusvaheline juhend GUM. Üldiselt vastavad selle alusel saadud määramatuse hinnangud enamiku rakenduste nõuetele, kuid praktikas esineb olukordi, mille korral GUM ei anna optimaalset lahendust. Üheks keerulisemaks küsimuseks on mõõteseeria keskmise alusel määratud mõõtetulemuse määramatuse hindamine, kui seeria tulemused omavahel korreleeruvad. Teiseks mitte vähem keeruliseks probleemiks komparaatori tulemuste hindamisel on süstemaatiliste efektide kindlakstegemine ja elimineerimine või siis vähemalt nende panuse arvessevõtmine mõõtemääramatuses. Mõlemad probleemid võivad tähelepanuta jätmisel viia mõõtemääramatuse ekslikule hindamisele. Antud uurimistöös väljatöötatud meetodid võimaldavad mõlemat ohtu vähendada ja neid saab rakendada ka teistes mõõtevaldkondades. Massi riigietaloni laboratooriumi mõõtetulemuste ja määramatuse hinnangute usaldusväärsust kinnitab hea kooskõla, mida on näidatud arvukatel rahvusvahelistel võrdlustel.A high-level well-working national measurement infrastructure is essential for competitiveness of country, for the advancement of science and technology, and for quality of life. Since 2001 in Estonia at the Central Office of Metrology, Metrosert, the national standards for mass, length, temperature and electric quantities are established at the internationally secondary level. National measurement standard usually represents the top level competence of the country in respective scientific-technical field. However, in order to use its capabilities effectively confidence in the measurement uncertainty and international equivalence of offered services is needed. Technical level and international equivalence of the standard are validated by international experts on the basis of inter-comparisons and peer evaluations, whereby measurement uncertainty is a key element for meaningful determination of the degree of equivalence between the standards and measurement results. Estonian standard laboratory for mass (NSLM) is realizing and representing the mass scale from l mg to 50 kg, being able to calibrate the mass and conventional mass value of the weights with the highest OIML E1 accuracy class. NSLM can test the conformity of magnetic properties of the weights to the requirements of the respective accuracy class. NSLM can calibrate the density of the weights in the range from 1 g to 2 kg. Mass laboratory is equipped with three automatic mass comparators, with more than 100 weights, and with many auxiliary instruments; laboratory is accommodated in air-conditioned measurement rooms with temperature and humidity control, and with filtered air. At the NSLM preferably four measurement models are used; these models are carefully validated for the whole relevant measurement range. For evaluation of the uncertainty in measurement for major part of instruments extensive calibration histories are available. Additionally, some special studies are conducted, in order to get better data base for uncertainty estimation as provided by routine measurements. Uncertainty of the weights representing the mass scale at the NSLM is estimated following the GUM standard procedures. In general, uncertainty evaluated according to GUM performs satisfactorily for majority of applications. Nevertheless, there are some situations in practice allowing improvement if sufficient measurement information is available. Not easy to handle is the effect of nonzero serial correlation. Another similarly complicated problem is revealing possible systematic effects in comparator readings in order to eliminate them or at least to take them into account in measurement result and uncertainty estimate. If not treated the uncertainty may be substantially underestimated. Methods proposed in this study will at least partly solve both problems and reduce risk of underestimation, and they are applicable in many other measurement fields. The agreement between the inter-comparison results presented by the NSLM and comparison reference values demonstrated to date shows that measurement methods, calibration procedures and respective uncertainty estimates developed and tested at the NSLM can reliably be applied in practice

Programmierbare Josephson-Arrays für Impedanzmessungen

An innovative way of networking two programmable Josephson arrays generating synchronous waveforms for impedance ratio measurements, as the first of its kind, is presented. This pioneering approach of the Josephson Impedance Bridges is far more flexible than conventional bridges at the same level of measurement uncertainty. Results prove that aside from having the capability of measuring over a wider frequency range, the Josephson bridge permits measurements on two impedances with any value of phase angle between them. In the two-terminal-pair Josephson bridge setup, measurements are made for a 1:1 resistance ratio at the 10-k level in the frequency range between 25 Hz and 10 kHz. Uncertainties reach to levels of better than a few parts in 108 and results agree to the values measured from conventional impedance bridges. Two methods for four-terminal impedance measurements have been investigated, the potential comparison circuit and the coaxial setup. Both methods are capable of measuring from DC to 6 kHz with uncertainties to 10−8. The four-terminal-pair coaxial setup has potential to decrease the relative uncertainty down to 10−9 once systematic errors are analyzed and canceled. Thermal converter measurements have been made to investigate the effects of transients on stepwise approximated sinewaves. Rms measurements show that transients limit the uncertainty to about 10−6 at 1 kHz. A simple model with an equivalent time constant is presented to evaluate the influence of different parameters on the shape of the transients. It has been experimentally established, at the 10−8 level of uncertainty for the determination of impedance ratios, that the variations of the transients in stepwise approximated waveforms can be neglected when using the fundamental component of rectangular waveforms. Quantization at up to 10 kHz has been confirmed by varying the bias current of the Josephson arrays resulting in constant resistance ratios within the measurement resolution.Ein innovativer Weg, zwei programmierbare Josephson-Schaltungen für Impedanz-Verhältnismessungen zu verknüpfen, wird erstmals in dieser Arbeit präsentiert. Dieser neuartige Ansatz einer Josephson-Impedanzmessbrücke ist flexibler als konventionelle Impedanzmessbrücken bei gleicher Messunsicherheit. Es wird gezeigt, dass neben der Möglichkeit, über einen wesentlich größeren Frequenzbereich zu messen, die Josephson-Impedanzmessbrücke auch Messungen sehr unterschiedlicher Impedanzverhältnisse und beliebiger Phasenwinkel erlaubt. In einer Zwei-Tor-Anordnung der Josephson-Impedanzmessbrücke wurden Messungen für ein 1:1 Widerstandsverhältnis bei 10 k im Frequenzbereich von 25 Hz bis 10 kHz durchgeführt. Die Ergebnisse stimmen mit denen einer konventionellen Messbrücke im Rahmen der Unsicherheit von wenigen 10−8 überein. Für eine Vier-Tor-Anordnung wurden zwei unterschiedliche Methoden untersucht, eine Spannungsverhältnisschaltung und eine koaxiale Vier-Tor-Anordnung. Letztere hat das Potential, Unsicherheiten von 10−9 zu erreichen, sobald systematische Fehler eliminiert sind. Um Effekte der Transienten in stufenförmig approximierten Sinuswellen zu untersuchen, wurden Messungen an Thermokonvertern durchgeführt. Diese Effektivmessungen zeigen, dass Transienten die relative Messunsicherheiten auf etwa 10−6 bei einer Frequenz von 1 kHz beschränken. Es wird ein einfaches Modell vorgestellt, das die Form der Transienten in Abhängigkeit der wesentlichen Parameter beschreibt. Experimentell konnte bei Impedanzverhältnismessungen mit einer relativen Messunsicherheit von 10−8 nachgewiesen werden, dass die Variation der Transienten in stufenförmig approximierten Wellenformen vernachlässigbar ist, wenn die fundamentale Komponente eines Rechtecksignals verwendet wird. Quantisierte Plateaus wurden bis zu Frequenzen von 10 kHz gefunden, bei denen die Variation des angelegten Stroms durch die Josephson-Schaltungen keine Veränderung des Impedanzverhältnisses zur Folge hatte

Development of laser spectroscopy for scattering media applications

Laser spectroscopy for both large and small spatial scales has been developed and used in various applications ranging from remote monitoring of atmospheric mercury in Spain to investigation of oxygen contents in wood, human sinuses, fruit, and pharmaceutical solids. Historically, the lidar group in Lund has performed many differential absorption lidar (DIAL) measurements with a mobile lidar system that was first described in 1987. During the years the lidar group has focused on fluorescence imaging and mercury measurements in the troposphere. Five lidar projects are described in this thesis: fluorescence imaging measurement outside Avignon, France, a unique lidar project at a mercury mine in Almadén, Spain, a SO2 flux measurement at a paper mill in Nymölla, Sweden, and two fluorescence imaging projects related to remote monitoring of vegetation and building facades characterization. A new method to measure wind speed remotely in combination with DIAL measurements is presented in this thesis. The wind sensor technique is called videography and is based on that images of plumes are grabbed continuously and the speed is estimated by the use of image processing. A technique that makes it possible to measure a gas in solids and turbid media, non-intrusively, is presented in this thesis. The technique is called gas in scattering media absorption spectroscopy (GASMAS) and has been used since 2001. The GASMAS concept means that a traditional spectroscopy instrument, based on tunable diode lasers, is used but the gas cell or optical path is replaced by a material that strongly scatters light. Mostly, wavelength modulation spectroscopy has been utilized. Four projects using the GASMAS technique to measure gases in fruit, wood, pharmaceutical solids, and human tissue are presented. Two applications have shown a great potential so far; to be able to diagnose the health of human sinuses and gas ventilation in sinuses, and to measure gas inside pharmaceutical solids. A performance analysis of the GASMAS technique is included. This thesis also presents a technique to suppress optical noise in fiber lasers and how to construct a compact tunable diode laser spectroscopy system based on plug-in boards for a standard computer