MK 19 Mod 3D Gyrocompass System

The accelerometer preamplifier amplifies the

what portion of this signal is actual tilt of the spin axis.

modulated 4900-Hz carrier output of the accelerometer

The signal from the accelerometer control loop, which

before its transmission by cable to the compass control

consists of acceleration plus tilt signals, is integrated in

cabinet. By increasing the signal power level before

the speed-tilt computer loop to obtain a velocity plus tilt

transmission, crosstalk (or cross modulation) and

signal. The velocity component of this signal is removed

spurious disturbances that would degrade the inherent

by subtracting north-south speed, which leaves only

accelerometer signal-to-noise ratio are prevented. Two

tilt.

such accelerometer preamplifiers are required per

system--for the meridian and slave gyros--and each

The accelerometer (fig. 4-42) is a pendulous mass,

contains its own power supply.

force feedback instrument that mounts directly to the

meridian gyro vertical ring. Its main components are the

proof mass, torque and backup plate, and pickoff, all

MK 19 MOD 3D GYROCOMPASS

SYSTEM

mounted to a common support.

The proof mass is a curved aluminum plate

The Mk 19 Mod 3D gyrocompass system is

suspended by cross-spring pivots and is the element

identical to the Mk 19 Mod 3C system with the

against which the torque acts. Attached to an extension

exception that solid-state devices are used in the

of the proof mass is the iron pickoff core.

follow-up amplifiers, switching, and control

assemblies.

The torque is similar to the gyro torquers. It is a

2-phase induction type with the control field windings

in series, opposing, and the fixed field winding excited

MK 19 MOD 3E GYROCOMPASS

from the A transformer wired in a Scott "T"

SYSTEM

arrangement. The torque is backed with a laminated iron

piece to improve the torque capability. The torque and

The Mk 19 Mod 3E gyrocompass system is

backup plate are encapsulated in plastic in such a

identical to the Mk 19 Mod 3D system with the

manner so as to enclose the proof mass.

exception that the compass has been modified to add an

optical cube used for alignment. This optical cube

The pickoff is a moving iron inductive-type

permits precise alignment of the compass during

transducer that detects relative motion between the

compass installation.

proof mass and the support. Excited with 4900 Hz to

In addition, the control cabinet has been modified

achieve frequency separation from the 400-Hz power

and a velocity interface unit has been added to permit

frequency, the pickoff output has magnitude and phase

satellite interfacing with the compass.

sense proportional to displacement from a null or level

position. This signal is amplified and converted to 400

MK 19 MOD 3R AND

Hz to drive the torque, which restores the proof mass to

3RC GYROCOMPASS

null.

SYSTEMS

The tilt plus acceleration output is the 400-Hz

torque control field voltage. Because the accelerometer

The Mk 19 Mod 3R gyrocompass is a factory rebuilt

cannot distinguish between tilt and acceleration, the

Mk 19 Mod 3, rebuilt to Mod 3A specifications. The Mk

output contains both components. The acceleration

19 Mod 3RC gyrocompass is a factory rebuilt Mk 19

component is withdrawn in the speed-tilt computer loop,

Mod 3, rebuilt to Mod 3C specifications.

leaving only the tilt component.

WATCH STANDING

The range of the instrument is

gram or a tilt of

2335 minutes, and the scale factor is 75 volts per gram

or approximately 23 millivolts per minute of tilt. The

Watch-standing procedures for the Mk 19 Mod 3

pickoff excitation is 0.5 volts, 4900 Hz, and the torque

gyrocompass systems are basically the same as for the

Mk 23 Mod 0 and Mod C3 systems.

fixed field excitation is 100 volts, 400 Hz.

4-44