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Monitoring zawartości wilgoci w murach ceglanych metodą rezystancyjną - dobór skali kalibracji czujników

Wójcik Robert, Kosiński Piotr, Misiewicz Joanna

Materiały Budowlane

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2023

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nr 3

38--41

PL

Na Uniwersytecie Warmińsko-Mazurskim w Olsztynie opracowano sondy impedancyjne przeznaczone do długoterminowego monitorowania zawartości wilgoci w murach ceglanych [1]. Jak wszystkie pomiary pośrednie, wykorzystanie przepływu prądu elektrycznego wymaga przeprowadzenia procedur skalowania urządzeń pomiarowych [2, 3, 4, 5, 6]. W artykule omówiono istotny problem, jakim jest dobór optymalnej wielkości wzorców wilgoci wykorzystywanych do kalibracji. Stwierdzono, że przepływy sygnałów prądowych wysyłane podczas pomiarów jednorazowych i cyklicznie powtarzane w ramach monitoringu zmieniają właściwości fizyczne kapilarno-porowatej struktury muru. Ustalono zasięg występowania interakcji sygnału elektrycznego z wilgotną strukturą badanego materiału. Określono minimalną wielkość wzorców przy jednoczesnym uwzględnieniu reprezentatywności wielomateriałowych struktur murowych. Ustalono również inne czynniki wpływające na dokładność kalibracji.

XX

At the University of Warmia and Mazury in Olsztyn there have been developed impedance sensors for long-term monitoring of moisture content in brick walls [1] in response to this demand. Similarly, as with all indirect moisture content measurements, the use of the electric current flow, also requires carrying out procedures for scaling measuring devices [2, 3, 4, 5, 6]. The article discusses the selection of the optimal size of moisture standards, what is undoubtedly an important problem of calibration procedures. It was found that the current signal flows, sent both during single measurements and cyclically repeated as part of monitoring, change the physical properties of capillary porous structure of the walls. The range of interaction of the electrical signal with the wet structure of the tested material was determined. The minimum size of the standards was specified, basing the representativeness of multi-material structures. Other factors affecting calibration accuracy have also been established.

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A study on the calibration of an HPM meter based on a D-dot sensor and logarithmic RF power detector

Jakubowski Jacek

Metrology and Measurement Systems

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2020

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Vol. 27, nr 4

673--685

EN

HPM meters are required for the assessment of fields generated by sources of high-power microwaves. Finding the inverse calibration curves for such instruments is important for ensuring accuracy. The procedure is relatively simple for meters consisting of linear devices but there can also be hardware solutions implementing nonlinear ones. The objective of the present work was to develop a convenient procedure to allow finding such a curve when the meter uses a D-dot probe and a power detector. For that purpose, the results of low voltage measurements describing the properties of the detector were first analysed. Then a software code was developed to estimate the RMS value of an incident field based on measured output and frequency response. The response was estimated with very low electric field. And finally, the performance of the proposed procedure was verified by tests conducted with high electric field in a TEM cell. High conformity of the output of the meter with fields of known values was demonstrated. The maximum error related to the meter range did not exceed 4%.

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Low cost attitude and heading sensors in terrestrial photogrammetry – calibration and testing

Kolecki J., Kuras P.

Archiwum Fotogrametrii, Kartografii i Teledetekcji

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2011

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Vol. 22

249--260

EN

Most of the contemporary terrestrial mobile mapping systems (MMSs) use tactical or navigation grade inertial measurement units (IMU) to determine the approximated angular exterior orientation (EO) elements of images. Navigation grade IMUs, usually integrated with GNSS receivers, are also used to determine the projection center coordinates. Recent researches show that using also a low-cost attitude and heading reference system (AHRS) or a low-cost IMU, satisfies the demands of certain photogrammetric applications. Our researches aim to evaluate the accuracy of low-cost devices suitable for constructing small, low-cost photogrammetric MMS. During our research two low-cost devices, providing information about image attitude and heading, were tested. The first one is the calibrated Ricoh G700SE GPS camera with an electronic compass and a level indicator. The second device is the Xsens MTi AHRS unit, comprising 3 MEMS (micro-electromechanical systems) gyros, 3 MEMS accelerometers and 3 magnetometers. For the testing purposes the AHRS was combined with the calibrated Nikon D80 SLR camera. The 3D AHRS magnetometer calibration was carried out using the manufacturer's software to compensate for the soft and hard iron effects. The images of three test fields were taken. The images of the first test field with signalized control points were used to determine the boresight rotation matrix of the AHRS. The bundle adjustment was solved separately for each camera and each test field to determine the true (reference) angular exterior orientation parameters. The differences between measured and calculated angles allowed to evaluate the accuracy of the measured angles. The tests results for the GPS camera show high residuals of measured azimuths, however its level indicator allows camera levelling with subdegree accuracy. The results obtained for the low-cost AHRS unit were significantly better, however over 2° residuals for yaw angle were also observed. The results prove the usefulness of the AHRS for constructing a small, hand-held MMS, whereas GPS camera azimuth measurements can be treated rather as a rough approximations in the photogrammetric network adjustment.