ETS-Lindgren HI-3604, User Manual

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23
Field Strength Measurements
Measurement of electric field strength, under a power line or near any other
source of electric fields, may be accomplished by supporting the HI-3604 on a
non-conductive tripod (Part Number 491009), such as that shown in Figure 4-1.
Be sure to orient the top surface of the sensor paddle towards the field source. It
is critical that the user not hold the instrument since this will significantly alter the
response of the HI-3604 providing an apparently enlarged field collecting surface
for the displacement current sensor, resulting in an erroneously high indicated
field strength. In addition, the presence of the operator's body will tend to perturb
the electric field that is being measured. The operator should remain
approximately one to two times their height away from the HI-3604 and observe
the readings via the use of the HI-3616 Fiber Optic Remote Control. The
instrument is supported with the digital readout facing upward; in this position,
the electric field lines which are directed downward toward the earth will strike
the correct side of the displacement current sensor resulting in an accurate
measurement of the field strength. Because of the physical asymmetry in the
displacement current sensor it is imperative that the front side of the sensor be
directed toward the electric field source.
Measurement of the electric field strength beneath power lines may also be
accomplished by laying the HI-3604 on its back directly on the ground, with the
sensor disk facing upward. In this orientation, the vertically polarized electric field
component is measured. When performing measurements with the instrument on
the ground, care must be exercised to insure that vegetation, such as tall weeds,
does not interfere with the field strength measurement due to the shielding
phenomenon discussed above. In either case, with the instrument elevated on a
tripod or laying on the ground, the HI-3604 should be oriented so that the long
axis of the body of the instrument is parallel to the conductors of the power line.
This orientation is necessary to reduce any instrument response to any horizontal
component of the electric field caused by the asymmetric physical shape of the
HI-3604. Figure 4-3 illustrates the correct orientation of the instrument relative to
the power line conductors.