ETS-Lindgren HI-3627, User Manual

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ets-lindgren.com Example Applications of the HI-3627 25
technique is to position the sensor at a point approximately one meter
from each room corner for the flux density measurement. This avoids,
to an extent, placing the sensor immediately next to wiring which may
be hidden within the walls of the room and which may yield
unrealistically high values of flux density compared to what most
individuals within the room might be exposed. A possible protocol for
making the measurements is outlined in the California Department of
Health Services paper on suggested protocol for measuring 60 Hz
magnetic fields in residences (3).
Surveys of the areas near electrical appliances will usually reveal
higher values of flux density due to the currents flowing within motors
or heating elements. This may influence the location of beds, and other
locations of extended occupancy. In characterizing the magnetic fields
near obvious sources, such as appliances, it is often helpful to
measure and record the flux density value at intervals of a few inches
(or centimeters) beginning near the surface of the device. These data
will help provide a perspective on the spatial extent of the elevated
field levels and the significance of the levels relative to other values
determined elsewhere within the home. Field measurements should
take into account the likelihood that individuals may have access to
areas where measurements are contemplated.
Because 60 Hz magnetic fields produced by the use of electricity within
the home are dependent on the magnitude of current flowing within
wires or the operation of appliances, flux densities will be seen to vary
with time, being greater when more electrical power is being used. For
example, when heating or air conditioning systems turn on or the
compressor within a refrigerator cycles on, the flux density will
increase. Measurements must take this condition into account. It is
recommended when taking measurements in a room, the meter be
watched for a period of time to observe for fluctuations in the indicated
value of flux density. After some experience, it may be possible to
relate the observed fluctuations to various uses of electricity within the
room.