ETS-Lindgren HI-4457 Isotropic Magnetic Field Probe (Archived) - Manual (Page 23)

Page — 18 HI n 4457 Manual
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.
Probe Power Supply
The HI n 4457 probe is powered by a sealed rechargeable
3.6 VDC NiCd battery, which drives both the analog and
digital power supplies: 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. The
power switch is controlled by a timer circuit. 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)
Archived 4/2/10