ETS-Lindgren HI-4455 Isotropic Field Probe (Archived) - Manual (Page 17)

HI-4455 Isotropic Electric Field Probe
© ETS-LINDGREN L.P. – August 2005
Revision D- Part No. H-600076 17
PROBE OPERATION
Receiver commands to the probe consist of the following:
• Send
reading
• Read battery voltage
• Zero
• Set sleep timer
• Switch range
• Read temperature
• Enable
axis
The signal flow within the probe is shown in the block diagram.
To measure field strength, three mutually orthogonal dipole antennas
(one per axis) are used to provide an isotropic response to the ambient
field. The signal from each axis is fed to a Schottky diode detector
operating in its Square-Law region. After filtering, the signals generated
by each axis are added vectorially: the resultant is fed to the
instrumentation amplifier, whose output feeds the selectable range/offset
stage.
NOTE: The HI-4455 does not allow the option of
measuring on an individual axis: all three axes are active
at all times.
For each of the four ranges, the selectable range and offset stage
provides a coarse analog zero for the measured signal. The output of
the range/offset stage is fed to the A/D multiplexer, then to the analog-to-
digital (A/D) converter itself.
After acquiring the composite three-axis signal, the microprocessor
commands the A/D multiplexer to read the battery voltage and
temperature sensing lines.
Data from the A/D converter is fed to the microprocessor, which
transmits it to the receiver.
The EEPROM stores all calibration data for the probe.
Archived 4/2/10