ETS-Lindgren HI-4455 Isotropic Field Probe (Archived) - Manual (Page 18)

HI-4455 Isotropic Electric Field Probe
© ETS-LINDGREN L.P. – August 2005
Revision D- Part No. H-600076
18
PROBE POWER SUPPLY
A sealed rechargeable 3.6 VDC NiCd battery, which drives both the
analog and digital power supplies, powers the HI-4455 probe: separate
power sources provide isolation between the analog and digital circuitry.
With the probe switch in the ARM position, battery voltage is applied to
the power switch, which routes this voltage to the power supply, enabling
the microprocessor. A timer circuit controls the power switch. The timer
monitors the fiber optic connector input line to determine whether the
probe has received a command during a specified period (several
seconds). If no command is received during this period, the timer signals
the power switch to disable the power supply and the microprocessor. In
essence, the probe goes dormant to conserve battery power: only the
fiber optic input circuitry remains active in order to detect new
commands. When the next command from the receiver reaches the
probe, power is reapplied automatically and the processor is reactivated,
"waking up" the probe.
NOTE: The probe uses volatile random access memory
(RAM). If, for any reason, power to the probe is lost, the
probe must be re-zeroed.
ZEROING
When the receiver sends a zero command, the probe must be in a zero
field environment. This is because the zero command causes the
multiplexer (via the processor) to perform a normal read cycle on the
composite axis signal. This procedure is executed for all ranges. When
the processor receives all the zero-field values, it stores them in a
special register; these values are subtracted from all subsequent
measurements. Therefore, a probe which is zeroed while it is not in a
zero field environment will give erroneous readings.
Archived 4/2/10