Built-in Test Equipment

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

reference output.

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.

supply.

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.

indicator.

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

module, transformer rectifier, and inverter assembly

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

temperature.

4-56