ETS-Lindgren HI-3604 ELF Survey Meter - Manual (Page 10)

Page -- 2 HI-3604 Manual
related to the external electric field strength. This type of
transducer possesses a flat frequency response and permits
accurate measurement of fields having significant harmonic
content with energy at frequencies above the fundamental of 50
or 60-Hz.
Surrounding the circular displacement current sensing disks is a
coil consisting of several hundred turns of fine gage wire. When
placed in an alternating magnetic field, a current is induced in
the coil which is proportional to the strength of the applied
magnetic field. Magnetic field strength is then determined by
measuring the voltage developed across the terminals of the
coil. While an unterminated loop will provide an output which is
directly proportional to the frequency of the magnetic field, the
HI-3604 employs electronic compensation circuitry which
results in a tailored frequency response that is flat in the
frequency range of importance to power frequency
measurements. This feature permits the HI- 3604 to be used in
environments having significant harmonic content and yield
accurate measures of the resultant fields. Broadband response
is required when measuring fields having significant harmonic
distortion such as may occur with electrical machinery.
The outputs of both field transducers are measured with a true
root-mean-square (RMS) detector. True RMS detection offers
accurate evaluation of fields having a variety of waveforms,
including non-sinusoidal waveforms. Thus, whether the field
being measured is produced by a near pure sine wave source,
like an electric power transmission line, or a highly non-
sinusoidal source, like a solid state light dimmer, the HI-3604
will yield consistent measures of the RMS field strengths.