Built-in Test Equipment
charging voltage is present as long as the 3-phase,
115-volt ac ship's power is available and turned on.
The BITE provides four types of built-in tests.
The unregulated 28 volts dc is applied to the 5-volt
These are hard-wired, software, software-initiated, and
and 13-volt regulators. The 5-volt regulator reduces the
software-monitored built-in tests. The hard-wired BITE
unregulated 28 volts dc to a regulated 5 volts dc, which
consists of test logic that is wired directly to the fault
is distributed to all using circuit cards and assemblies.
circuits. Fault signals that start the automatic shutdown
sequence are hard wired. The software built-in tests are
The 13-volt regulator reduces the unregulated 28 volts
tests that are controlled by the processor, rather than by
dc to a regulated 13-volt dc level, which powers the
hard-wired logic circuits. The software-initiated BITE
DC/DC module. The 13-volt regulator is turned on
consists of hard-wired logic circuits that are activated
before the 5-volt regulator to allow the DC/DC module
by the processor. The software-monitored BITE circuits
and equipment to stabilize before the distribution of the
are not wired directly to fault circuits. Instead, the
5 volts dc. The DC/DC module provides output voltages
monitored parameters are compared to predetermined
of +28 voks, -28 volts, +15 volts, -15 volts, +20 volts
parameters known to the software. If the monitored
floating, +50 volts, and +50 volts floating. Floating
parameters are determined to be wrong, the appropriate
indicates those voltages are isolated from power ground.
fault indicator is energized; and if the fault warrants, the
gyro is shut down. When any fault is detected by the
Single-phase, 115-volt ac ship's power is applied to
BITE, the ALARM indicator on the control indicator
the gyro by an EMI filter, a relay, and the SYN REF
and the appropriate fault indicator are energized.
(synchro reference) circuit breaker. The single-phase,
The fault indicators are located on the control
115 volts ac provides power for the inverter magnetic
indicator. They are labeled FAULT AIR, FAULT DI,
module, internal resolver reference, and a vital heading
FAULT CTR, FAULTPS, BATIERY STAT, BATTERY
OPR, FAULT BFR, HDG FAIL, FAULT IMU, and
The gyrocompass will automatically switch to
ALARM. These indicators serve to lead the operator to
battery operation when the 3-phase or single-phase
the failed area of the system.
ship's power input is lost, loses a phase, or exceeds
FAULT INDICATORS.-- The FAULT AIR
prescribed voltage or frequency tolerances. If the
indicator is energized when an overtemperature
single-phase input is lost or exceeds tolerances, the
condition occurs in the power supply section of the
system will shift to inverter backup.
control power supply, synchro signal amplifier, or the
IMU. When this condition exists, an overtemprature
The gyro is turned on and off by logic circuits in the
no-go signal is sent to the control monitor, which starts
control monitor, which is located in the control power
the automatic power shutdown sequence.
The processor monitors the control signals from the
Certain conditions will cause the control monitor to
control indicator. When erroneous control output
automatically turn the gyro off. These conditions are
signals are detected, the processor sends out signals that
overtemperature, power supply fault, IMU fault, and
energize the FAULT DI indicator and the ALARM
battery under voltage when operating on the battery.
When automatic shutdown occurs, the control monitor
The circuit cards, in the control section of the
turns the gyro off as if the MODE switch were turned to
control power supply, are monitored and tested by the
the POWER OFF position, with one exception. Built-in
processor. When a circuit card fails, the FAULT CTR
test signals are applied to the control power supply to
and ALARM indicators on the control indicator are
energize the proper fault indicators and alarms.
energized. A combination of the six indicators, located
inside the control power supply, will be energized,
BITE circuits in the control monitor continuously
indicating which circuit card is faulty.
check the 5-volt regulator, 13-volt regulator, DC/DC
BITE logic circuits in the control monitor
outputs for over- and undervoltage conditions. hey
continuously monitor the 5-volt regulator, 13-volt
also monitor the frequency and voltage of the 3-phase
regulator, DC/DC module, battery charger, and battery
and single-phase, 115 volts ac and the power supply
set for overvoltage and undervoltage conditions. If an
undervoltage condition in the battery charger occurs, the