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Grgic G.,Metrology Institute of the Republic of Slovenia | Pusnik I.,University of Ljubljana
International Journal of Thermophysics | Year: 2011

A thermal imager with a microbolometer focal plane array (FPA) detector which does not require cooling is a relatively new type of instrument. With increasing use of thermal imagers for absolute temperature measurements, there is also an increasing need for their calibration. Five thermal imagers from three manufacturers were evaluated to identify parameters which affect their performance for accurate temperature measurements. Evaluation methods and measurements of parameters such as accuracy, temperature resolution, drift between internal calibration, non-uniformity, size-of-source effect, and distance effect are discussed. Based on the results, it is indicated which parameters should be evaluated in the calibration procedure as well as the uncertainty budget. The suitability of a blackbody for calibration was also addressed, especially in terms of dimensions related to the field of view of a thermal imager at the minimum focal distance. © 2011 Springer Science+Business Media, LLC. Source


Lapuh R.,Metrology Institute of the Republic of Slovenia | Lapuh R.,Slovenian Institute of Quality and Metrology
IEEE Transactions on Instrumentation and Measurement | Year: 2015

This paper describes an algorithm for estimating the frequency, amplitude, and phase of the fundamental component in harmonically distorted waveforms. The algorithm minimizes the phase difference between the sine model and the sampled waveform by effectively minimizing the influence of the harmonic components. It uses a three-parameter sine-fitting algorithm for all phase calculations. The resulting estimates show up to two orders of magnitude smaller sensitivity to harmonic distortions than the results of the four-parameter sine fitting algorithm. © 1963-2012 IEEE. Source


Lapuh R.,Metrology Institute of the Republic of Slovenia | Lapuh R.,Slovenian Institute of Quality and Metrology | Pinter B.,Slovenian Institute of Quality and Metrology | Voljc B.,Slovenian Institute of Quality and Metrology | And 2 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2011

Oscilloscopes are typically calibrated using special signals for each parameter. A common method using only sine-wave signals and analysis of sampled data is proposed to calibrate all major parameters of a digital sampling oscilloscope, greatly simplifying the calibration procedure while attaining lower uncertainties. The procedure can be also fully automated as the readout from the oscilloscope screen is no longer needed. © 2006 IEEE. Source


Voljc B.,Slovenian Institute of Quality and Metrology | Lindic M.,Slovenian Institute of Quality and Metrology | Pinter B.,Slovenian Institute of Quality and Metrology | Kokalj M.,Slovenian Institute of Quality and Metrology | And 3 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2013

This paper describes development and evaluation of a new coaxial current shunt for the nominal current of 100 A. The current shunt has been developed for both ac-dc transfer difference measurement and direct measurement of ac current. The direct ac measurement method was proposed by the Slovenian Institute of Quality and Metrology in 2002 and has now been expanded up to 100 A with the shunt described here. The forced air cooling system was implemented and evaluated to improve the shunt characteristics while keeping the current shunt resistors well within the safe operating range. © 2013 IEEE. Source


Lapuh R.,Metrology Institute of the Republic of Slovenia | Lapuh R.,Slovenian Institute of Quality and Metrology | Clarkson P.,Slovenian Institute of Quality and Metrology | Pogliano U.,INRIM - Istituto Nazionale di Ricerca Metrologica | And 2 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2011

The measurement of many signal parameters using digital sampling relies on synchronization between the sampling clock and the signal under analysis. Deviations in the frequency of the measured signal from that expected can lead to significant measurement errors. Many techniques for overcoming these problems have been developed. Appraisals of the performance of these algorithms usually involve relatively benign steady-state signals, and the treatment is often heavily mathematical. This paper describes the testing of several algorithms for accurately recovering frequency and harmonic amplitude and phase information from mains-borne waveforms. This paper focuses on their practical use while avoiding abstract mathematical concepts. © 2006 IEEE. Source

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