Due to the growing number, diversity and spreading of magnetic field sources, an increasing need to determine the field levels of human exposure has arisen. Some of the most encountered sources are the overhead power lines (OPL) and the determination of spatial and temporal variation of the magnetic fields produced by OPLs is a challenge. In this paper a hybrid method for the estimation of the temporal and spatial distribution of the magnetic flux density B caused by OPLs, based on experimental measurements and on numerical and analytical simulations, is presented. Thus, using a small number of simultaneous spot measurements correlated with a long-term survey, maps of the magnetic flux density distribution on extended areas are established, for several time instances. The proposed method is verified using two sets of different measurements and the results obtained through simulation. The difference between the estimated and simulated values of B is under 5.5%, which is considered acceptable considering that B spans over a large set of values (724 nT ÷ 1375 nT) in the location of the long-term survey procedure. The possibilities and limitations of the proposed method are discussed.

In this experimental work we assessed the low-frequency magnetic field strengths in several areas of hospital’s environment: Intensive Care Unit, Orthopedic Surgery Room and Ultrasound Scanner Room. The study referred both to electromagnetic compatibility and electromagnetic biocompatibility issues. The highest value of the magnetic flux density was identified in the ultrasound scanner room, namely 6,985 $\mu$T, near an electromagnetic filter. The recorded values are below 7% of the maximum admissible values according to the ICNIRP, however in all three investigated areas we recorded values above 0,4 $\mu$T, which represents a health risk for long-term exposures, especially for children.

In this paper we conducted a study referring to survey of background magnetic field in a laboratory of Electrical Engineering Faculty, where students carry out didactic activity. Based on three sets of measurements made in the 2017-2023 period, a characterization of the main field sources and the background magnetic field was performed. During this period, the power supply network has suffered some changes, and in terms of the used instruments, it was switched from spot measurement performed with commercial instruments to continuous long-term surveys performed with automatic survey systems made and calibrated by authors. In addition to considering the spatial variation of the magnetic field, the study determines and analyzes the temporal variations of the background magnetic field, namely the daily, weekly and monthly variability. Thus, a great temporal variability of the magnetic field was identified with the week days and even months, can be reached in the ratios between the magnetic field averages on the week days and on the months of the year of order 4/1 or even 5/1.

In this paper we presented some measurements of the low frequency magnetic field from indoor distribution substation. Using two automatic measuring instruments we made both spot measurement and automatic long-term survey presenting the spatial and temporal variability of the magnetic field in five areas with indoor distribution substation. Correlating the time of spot measurement, with that of automatic survey we estimate the magnetic field values to reduce the errors due to the temporal variation. With the values obtained after estimating the field, we draw maps for the entire zone of an indoor distribution substation. The results were compared with the maximum permissible limits by national and international standards and we found that they were not exceeded. However, in all five areas the values of the magnetic field were above the threshold of 400 nT taking into account long-term exposure, which can lead to biological effects on health, especially for children.

In literature, there are two methods of distance measurement using video cameras: active and passive. Active methods use additional hardware to emit light beams from various configurations, and passive methods use light from the camera’s lens. Passive methods may use one or more camcorders. In the latter case, detection methods of an object are known based on the correlation with the focusing position of the focus lens and the identification of the image with maximum clarity. This article highlights solving some problems in this field by increasing the number of calibration states compared to the number of steps the focus lens can perform and implicitly increasing the measurement accuracy. The distance measurement method based on weighted average, according to the study conducted, comprises a calibration stage and a measurement stage.