XIX Sympozjum Srodowiskowe PTZE - materialy.pdf

XIX Sympozjum PTZE, Worliny 2009
Finally they do not give us information how important are all objects placed in the proximity
of exposed person. Moreover standards and accepted procedures do not specify these
conditions. IEEE recommends [2] to use a Human Equivalent Antenna what is the proper
solution at the plane wave condition [3]. Person with manpack radio on his shoulders is
always in the near field region of the antenna. Because of that the Human Equivalent Antenna
is useless for measurements of induced currents caused by manpack radio.
Solution
The goal of this study was to set conditions for induced current measurements in the body of
manpack radio operator. The measurements have been performed with clamp-on current probe.
The clamp-on current probe has been chosen because it is less responsive for ground
conductivity and ground surface texture than platform meter. The induced currents have been
measured in both ankles of three volunteers operating a few FM manpack radios in the
frequency range 1,5 – 100 MHz. Exposed persons differ in height from 1,60 to 1,85 m. The
currents have been measured in three typical for radio operator body configurations: 1) radio on
the shoulders, 2) radio on the ground, operator stands beside, 3) radio on the ground, operator
squats or kneels beside. Additionally we have examined if the grounding of the radio matters
and how the object placed in the proximity of the radio disturbs the measurements. These
objects were a concrete wall, a tree and a car.
Conclusion
There is no need to look for a special or average person to measure induced currents in his
ankles, we do not see meaningful differences between our radio operators.
The position of operator during the transmission has a great impact on current induced in his
body, the values of currents in standing positions were almost twice as big as in squatting
position or kneeling.
The grounding of the radio is the key factor, the values of currents induced in the ankles
dropped three to four times after the radio had been grounded.
The objects in the nearness are not important unless they are conductors, but the
measurements in the proximity of the car showed that we should keep distance of 3 to 5
meters from such objects.
References
1. Directive 2004/40/EC of The European Parliament and of The Council of 29 April 2004 on
the minimum health and safety requirements regarding the exposure of workers to the risks
arising from physical agents (electromagnetic fields).
2. IEEE C95.3-2002 Recommended Practice for Measurements and Computations of Radio
Frequency Electromagnetic Fields with Respect to Human Exposure, 100 kHz-300 GHz.
3. Poljak D., Choy Y. T., Gandhi O., Sarolic A., Human equivalent antenna model for transient
electromagnetic radiation exposure, IEEE/EMC Transactions 2003, vol. 45, iss. 1, pp. 141 – 145
4. Rozporządzenie Ministra Pracy i Polityki Społecznej z dnia 29 listopada 2002 r. w sprawie
najwyższych dopuszczalnych stężeń i natężeń czynników szkodliwych dla zdrowia
w środowisku pracy.
5. Wilen J., Mild K.H., Paulsson L-E., Anger G., Induced current measurements in whole body
exposure condition to radio frequency electric fields, Bioelectromagnetics, 2001, vol. 22 iss. 8,
pp. 560 – 567.
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