Figure 4-42.--Accelerometer control loop.

An additional circuit called a fault protector has

Securing the Mk 19 Mod 3B

been added. This unit receives inputs from the current

Gyrocompass

and voltage sensing circuits and sends an output or fault

The procedures for securing the Mk 19 Mod 3B

signal to the inverter drivers to expedite correction for

gyrocompass are the same as for the Mk 19 Mod 3A

overcurrent or other output faults.

gyrocompass.

Another major change in the Mk 19 Mod 3C

compass is the replacement of the electrolytic level in

the gravity reference system (Mk 19 Mod 3A and Mod

MK 19 MOD 3C GYROCOMPASS

3B) with an accelerometer. The accelerometer is a more

SYSTEM

accurate detector than the electrolytic level.

The Mk 19 Mod 3C gyrocompass system uses a

The meridian gravity reference system of the 3A

modified version of the static standby power supply

gyrocompass was discussed earlier in this chapter. In

used in the Mk 19 Mod 3B. This modified version,

modification 3C, the system consists of two closed-loop

known as the static power supply, is used as the primary

systems: the accelerometer control loop and the

power supply as well as the standby supply for the

speed-tilt computer loop (fig. 4-41). The system detects

compass. The static power supply receives 115-volt,

any horizontal deviation of the gyro spin axis and

400-Hz power from the ship's supply and, in turn,

supplies a signal proportional to the amount of tilt to the

supplies the compass with a highly reliable 3-phase,

meridian gyro azimuth and leveling control systems.

115-volt, 400-Hz power. If the ship's supply fails or falls

The accelerometer senses any accelerations in the

below 112 volts, the static power supply automatically

north-south plane as well as tilting of the gyro spin axis.

receives its power from the storage batteries.

The accelerometer control loop cannot distinguish

between tilting and accelerations, and its output signal

Another feature incorporated in the static power

to the speed-tilt computer contains acceleration and tilt

supply is a servicing switch on the inside of the panel

signals. The output signals would be basically the same

door. When the servicing switch is in the OFF position,

for northerly accelerations as for a tilt of the spin axis

the incoming ship's supply and the battery supply are

broken. When the servicing switch is in the READY

The speed-tilt computer accepts the output of the

position, the ship's supply and the battery supply circuits

accelerometer control loop (fig. 4-42) and determines

are lined up for normal operation.

Figure 4-42.--Accelerometer control loop.

4-43