ETS-Lindgren HI-2200 RF Survey Meter - Manual (Page 38)

38 | Application
Probe Support Structures
It is very important to keep conductive objects away from the HI-2200 RF Survey
Meter while measuring. Any conductive objects in the proximity of the probe may
distort the field and compromise measurement accuracy. If the application
requires measurements from a fixed position, always mount the probe on a
non-metallic platform using non-metallic screws. The optional ETS-Lindgren
Holaday H-491009 Tripod provides an adjustable, dielectric support for the
H-2200. See Optional Items on page 11 for more information.
Averaging
When evaluating electromagnetic field measurements, proper averaging of data
is an important part of the measurement process. Two aspects of averaging
when measuring electromagnetic fields should be considered.
First, how is the data actually averaged? In simple or LINEAR averaging, each
value of a group of field intensity readings is summed and the sum divided by the
total number of readings in the group. This type of averaging is more typically
used for lower frequency measurements (below about 100 kHz) when a safety
guideline or standard allows averaging.
At higher frequencies (typically above about 100 kHz), the primary metric of
interest is the energy absorption into the body. To most accurately define these
exposures, it is necessary that averaging be proportional to power density (more
accurately plane-wave-power-density) which is proportional to the square of the
field intensity (field-strength-units-squared). With the HI-2200, this type of
averaging is described as RMS (root mean square) averaging. In this mode,
each of the individual field intensity values is squared and these squared values
summed. This sum is divided by the total number of values and the square root
of this result calculated to indicate field strength values. The resulting number is
the RMS average value. When the displayed units are in power density, linear
and RMS averaging provide the same results.