DRAFT Recommended Practice for Measurements and ...

1/29/98 6 C95.3-1991 Revision — 2 nd Draft
10/98 Draft
Subcommittee 1 on Evaluation Techniques and Instrumentation was originally organized
on April 7, 1960, to establish specifications for techniques and instrumentation used in
evaluating hazardous radio frequency (RF) radiation. In June 1985 the scope was
clarified and the purpose was extended to establish specifications for techniques and
instrumentation to be used in evaluating RF hazards to mankind from exposure to
manmade sources of EM radiation or from the exposure of volatile materials and
explosive devices to such radiation. It is not intended to include infrared, visible,
ultraviolet, or ionizing radiation.
Although the subcommittee's scope includes hazards resulting from exposure of
flammable volatile materials and explosive devices to EM radiation, this document is
devoted exclusively to personnel hazards. This is because the necessary specifications
and definitions pertaining to fuels and explosive devices are still being developed, and
there are implications that the instrumentation requirements may be substantially
different from those addressed here. However, the measurement techniques and
instruments described here are applicable to the measurement of fields in the vicinity of
flammable materials and explosive devices, even though exposure standards for these
situations have not been established.
1.2 Frequency Range.
The techniques and instrumentation specified herein are useful for field measurements
over the frequency range of approximately 300 kHz to 100 GHz. 3 No single
measurement technique or instrumentation arrangement is valid over the wide frequency
range covered by this recommended practice. In general, measurement techniques and
instrumentation developed for use in the frequency range above about 300 MHz only
measure the electric field strength. Magnetic field strength measurements are, however,
required to evaluate near field hazardous situations at frequencies below 30 MHz. Here,
measurement of both the electric and the magnetic field strength is required within one
wavelength of the source. A series of commercially available instruments has been
developed for this purpose. For body currents, measurements can be made with simple,
portable laboratory instruments over the frequency range of 0 to about 100 MHz. SAR
can be measured using RF-transparent temperature sensors over the frequency range
of 0 to about 10 GHz. Above this frequency, energy absorption is confined to the surface
of a biological system. Thermographic cameras can be used to measure the surface
SAR up to about 300 GHz.
1.3 Quantities and Parameters to be Measured.
For frequencies above 300 MHz, and for measurements performed at distances from the
source greater than a 2 /λ with a probe whose dimensions are much less than a, power
density (W) is usually a meaningful quantity that has been widely adopted as a hazard
indicator (a is the largest dimension of the effective aperture of the source, and λ is the
wavelength). However, power density is difficult to determine, except in cases of
stationary, single-component, plane-wave fields of known polarization. In fact, no existing
instrument actually measures power density directly; all measure one or more
3 These frequency limits should not be considered rigid, but are given as a general guide. Normally, a
given instrument does not abruptly become invalid at a specific frequency; rather its accuracy, or
sensitivity, or both, deteriorate over some frequency range until finally it is no longer usable. For example,
an instrument designed for the lower frequencies may cover the entire broadcast band down to 0.5 MHz.
One should be aware of the frequency limitations of a given instrument when using it.
Copyright © 1998 IEEE. All rights reserved. This is an unapproved IEEE Standards Draft,
subject to change.