ETS-Lindgren HI-3702, User Manual

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Functional Theory of Operation
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5.0 Functional Theory of Operation
Following is a functional theory of operation for the HI-3702 Clamp-on Induced
Current Meter. The objective is to enhance user understanding of the theory
behind the design to aid with the operation and maintenance of the HI-3702.
The HI-3702 is designed to measure RF induced current flowing through the
ankles or arms of the body under test, even while walking or climbing. The fiber
optically coupled readout/control unit does not perturb the measured RF field or
the current distributions. The sensor is a ferrite split core current transformer. The
signal generated by the sensor is amplified by 10 dB to 50 dB depending on the
range that is selected. There is 20 dB of linearity for each range. This signal is
applied to a True RMS Thermal RMS to DC Converter. The DC voltage output of
the True RMS Thermal RMS to DC Converter is applied to a 12 bit
A/D converter. This digital representation of the DC voltage is read by the
microprocessor, converted to a number that is representative of current being
sensed, and transmitted through the fiber optic interface to the HI-4416 Digital
Readout/Control Unit.