ETS-Lindgren HI-3603 VLF Survey Meter - Manual (Page 34)

HI-3603 VDT/VLF Survey Meter
© ETS-Lindgren, August, 2005
Revision E, Part # H-600042
34
CHARACTERIZING OPERATOR EXPOSURE
Measuring operator exposure to VDT electric field emissions
requires that the HI-3603 be supported with a non-conductive
holding device. This is to reduce the influence of the surveyor on
the measure of fields incident on the VDT operator. The strength
of the electric field actually incident on the operator is a function
of the anatomical area of the body and the geometry of the
operator's body with respect to the VDT and other objects in the
room. Generally, the unperturbed field where the operator is
normally located will be less than the field incident on the
operator. Also, the field strength will vary strongly with distance
away from the body. For these reasons, the most accurate
measure of operator exposure is obtained when the HI-3603
sensor paddle is placed in contact with the operator's body but
while being held with a non-conductive holder by the individual
performing the survey.
In practice it is sometimes difficult to obtain the required
measurement simply because the LCD screen may be hidden
from view because it is so close to the VDT operator. There are
two approaches which can be taken in this case. (1) Perform the
measurement a fixed but short distance in front of the operator
so that one can view the LCD screen; (2) make use of the
optional Model HI-3616 Fiber Optic Remote Control and have
the VDT operator conduct a self-measurement.
In the first case, a fixed spacer made from foam plastic (Holaday
Industries, Inc. part number 470388) may be used. The spacer
fits over the sensor paddle and permits a uniform spacing of 5
cm between the sensor surface and the operator's body.
In the latter case, the VDT operator holds the HI-3603 directly
against their body and the surveyor via the fiber optic link reads
the measured electric field value remotely. This method of
determining VDT operator electric field exposure is superior in
that it minimizes the influence of the surveyor on the
measurement process. Also, when the operator performs this
self-measurement, the HI-3603 may be held directly without the
non-conductive holder since the electric field lines are
terminating on the operator's body anyway. Figure 11
demonstrates the HI-3603 being used in the self-measurement