## 1 Introduction
### On-Body Data Loggers in EMF Monitoring  
However, for various reasons the variability of the EMF level affecting workers during their shift is also considered. The use of portable, battery-powered equipment with internal memories for recording large time series of measured EMF samples seems to be promising in this respect. Personal exposure meters (PEM), i.e., autonomous data loggers worn on the body, allow the exposure to EMF to be measured in terms of variability over time, i.e., EMF exposure time-pattern, which is caused by the activity of the worker who is wearing PEM and fluctuations in emissions from the source. The conditions of taking measurements using wearable PEMs significantly differ from the standardized methods of evaluating EMF exposure. The protocol of using wearable PEM should therefore specify how to compensate for specific factors causing the measurement results to differ from the parameters of the unperturbed EMF, which are subject to the legal limits set for the purposes of assessing human exposure [8; 9; 11; 12; 13; 14]. Previous studies described in the research literature indicate that this technique is most often used in research regarding the characteristics of exposure to RF EMF emitted by radio communication systems [16; 17]. The commercially available PEMs that are sensitive to RF EMF (more precisely E-field sensitive devices) allow broadband or narrowband (frequency selective) measurements of exposure caused by electromagnetic emissions from various wireless radio communication systems to be investigated [18]. The basic parameters of RF EMF data loggers commonly used for various research purposes are given in Tables 2 and 3[19; 20; 21; 22]. All commercially available PEMs are designed for isotropic measurements with omnidirectional characteristic obtained by three axis-oriented internal RF EMF sensors. According to technical specifications, a deviation of isotropic PEMs sensitivity does not exceed 1.5 dB (19%). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Parameter**} \\ \cline{2-6}
**Type of PEM,** & **Frequency** & **E-Field** & **Sampling** & **Dimensions,** & **Weight,** \\
**Manufacturer (Country)** & **Band, MHz** & **Measurement** & **Rate, s** & **cm** & **g** \\ \hline RadMan 2 XT, & & & up to 200\% of & & \\ Narda (Germany) & 0.9–60,000 & & WELs & 0.03 or 1 & 17 \(\times\) 5 \(\times\) 3.5 & 190 \\ \hline RadMan 2 LT, & & & up to 200\% of & & \\ Narda (Germany) & 50–8000 & & WELs & 1 & 17 \(\times\) 5 \(\times\) 3.5 & 190 \\ \hline WaveMon RF-8, & & & up to 300\% of & & \\ Wavecontrol (Spain) & 0.3–8000 & & WELs & 1–3600 & 17 \(\times\) 4.5 \(\times\) 3.5 & 190 \\ \hline WaveMon RF-60, & & & up to 1000\% of & & \\ Wavecontrol (Spain) & 0.1–60,000 & & WELs & 1–3600 & 17 \(\times\) 4.5 \(\times\) 3.5 & 190 \\ \hline EME Guard, & & & & & \\ MVG (France) & 27–40,000 & 5–200 V/m & 1–255 & 17 \(\times\) 6 \(\times\) 3.5 & 300 \\ \hline EME Guard Plus, & & & & & \\ MVG (France) & 1–40,000 & 5–350 V/m & 1–255 & 17 \(\times\) 6 \(\times\) 4 & 300 \\ \hline \hline \end{tabular} Note: applied workers exposure limits (WELs) were set by ICNIRP’1998 [8] and Directive 2013/35/EU [5].  
\end{table} 
Table 2: Basic parameters of common broadband PEMs sensitive to RF EMF (according to manufacturers’ data) [19; 20; 21]. Various researches performed using RF EMF data loggers, followed different measurement procedures, developed on an ad hoc basis for the needs of particular research projects, meaning that there is no unified approach in this area with common consensus [23; 24; 25; 26]. RF EMF measurements with PEMs, especially narrowband (for example allowing the recognition of EMF sources), may bring various advantages over standardized measurements.