## 1 Introduction
### On-Body Data Loggers in EMF Monitoring
However, the results of such measurements are affected by the significant impact from the proximity of the human body on the measured EMF, such as the \"shielding effect\" to the measured EMF caused by the body, or the anisotropy of the measurement probes (sensors) when the equipment is used in a wearable form [26; 27]. The results of published research indicate that the use of single-location wearable RF EMF measurement equipment leads to an underestimation of exposure compared to what is measured by distributed multi-location equipment (for example, measurements with a twin-probe system, covering the operating frequencies of radio communication EMF sources, located at the front and back of the human body) [23; 24; 25]. In the case of commercially available equipment, this problem can be solved by using a cluster of several time-synchronized recorders, placed at various locations on the wearer's body [28]. As mentioned, the procedures for using wearable PEMs have so far been arbitrary and different for individual research projects regarding monitoring exposure of the population. For example, in order to avoid the effect of shielding RF EMF by the human body, the E-field probes were placed on an insulating stick above the subject's head [29]. The torso was assumed to be the primary relevant location for PEMs [23; 24; 25; 26]. The limbs, neck and head were evaluated as having limitations for wearing regular EMF data loggers there, because their movement during measurements could affect the measurement results [23]. Another proposed method for limiting the influence of the human body on the measurement result of RF EMF is the calibration of measurement equipment in an anechoic chamber, when it is located on a human body [24]. In the studies on measuring environ \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{5}{c}{**Parameter**} \\ \cline{2-7}
**Type of PEM,** & & \multicolumn{2}{c}{**Number of**} & \multicolumn{2}{c}{**E-Field**} & \multicolumn{1}{c}{**Sampling**} & \multicolumn{1}{c}{**Dimensions,**} & \multicolumn{1}{c}{**Weight,**} \\
**Manufacturer** & **Frequency** & **Band, MHz** & **Bands** & **Range, V/m** & **Rate, s** & **cm** & **g** \\  & & & **(Channels)** & & & & \\ \hline ESM-140, & & & & & & & \\ Satimo (France) & 88–2480 & 8 & 0.001–0 & 0.5–10 & 12 \(\times\) 4.5 \(\times\) 3 & 87 \\ \hline EMF SPY 121, & & & & & & & \\ Satimo (France) & 88–2450 & 12 & 0.05–10 & 4–255 & 19 \(\times\) 10 \(\times\) 7 & 450 \\ \hline EME SPY 140, & & & & & & \\ Satimo (France) & 88–5850 & 14 & 0.01–5 & 4–255 & 17 \(\times\) 8 \(\times\) 6 & 410 \\ \hline EME SPY 200, & & & & & & \\ MVG (France) & 87–5875 & 20 & 0.05–6 & 2–255 & 17 \(\times\) 8 \(\times\) 6 & 440 \\ \hline EME SPY & & & & & & \\ Evolution, MVG (France) & 87–5875 & max 20 & 0.05–6 & 2–255 & 18 \(\times\) 7 \(\times\) 5 & 520 \\ \hline ExpoM-RF3, & & & & & & \\ Fields at Work (Switzerland) & 87–5875 & 16 & 0.005–6 & 3–6000 & 16 \(\times\) 8 \(\times\) 5 & 320 \\ \hline ExpoM-RF4, & & & & & & \\ Fields at Work (Switzerland) & 50–6000 & max 25 & 0.005–6 & 3–6000 & 16 \(\times\) 8 \(\times\) 5 & 360 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Basic parameters of common narrowband (selective, multi-channel) PEMs sensitive to RF EMF (according to manufacturers’ data) [21; 22]. mental EMF disturbed by the body of a PEM wearer, the use of equipment calibrated in an anechoic chamber as an on-body wearable, allowed the error of exposure evaluation to be reduced to 3.2 dB (i.e., 1.5-times; 150%)--compared to 7 dB (i.e., 2.2-times; 220%)--estimating the case of using regular calibration of the measuring equipment in the unperturbed field (in an empty anechoic chamber).