Figure 10-10.--L coil.
MANUAL CURRENT CONTROL
for vertical induced magnetization. However, if the
FP-QP coil is used to provide vertical induced
compensation, its coil field strength must be changed
Many of the older (prior to the mid-1950s)
when the ship's magnetic latitude changes.
three-coil degaussing installations and all installations
with only an M coil have operator current control.
These installations were fabricated and installed by the
shipbuilders. They were never assigned type
designations. Manual or operator control is necessary
because an operator must adjust the degaussing coil
The L (longitudinal) coil (fig. 10-10) consists of
currents when they have to be changed due to a change
loops in vertical planes parallel to the frames of the ship.
in the ship's heading or magnetic latitude or both. In
The L coil is always used when compensation for the
such installations, roll and pitch compensation is not
pitch of the ship is required. The function of the L coil
is to counteract the magnetic field produced by the ship's
longitudinal permanent and induced magnetization.
The equipment controls power obtained from
The L coil is more difficult to install than the F and Q
constant voltage dc generators in some installations and
coils or FI-QI and FP-QP coils; however, it provides
from degaussing motor generators in other installations.
Coil currents are set by adjustment of the rheostats. The
the longitudinal magnetization of the ship. The L coil is
rheostats cnfigured in series with the degaussing coils
commonly used in minesweeper vessels.
when power is obtained from a constant voltage source
and in series with the generator field when
The longitudinal induced magnetization changes
when the ship changes heading or magnetic latitude, and
manually operated and motor-driven rheostats are used.
the L-coil current must be changed accordingly.
For each of the ship's degaussing coils, the required coil
currents, the various magnetic latitudes, and major
ship's headings are obtained from the degaussing charts
in the ship's degaussing folder. These current values are
determined for one latitude and calculated for other
The A (athwartship) coil (fig. 10-11) has loops in the
latitudes during calibration ranging. The current values
vertical fore-and-aft planes. The function of the A coil
given in the degaussing folder for the various zones of
is to produce a magnetic field that will counteract the
operation represent the sum of the induced field and
magnetic field caused by the athwartship permanent and
perm field currents.
athwartship induced magnetization. Since the
athwartship induced magnetization changes when the
AUTOMATIC CURRENT CONTROL
ship changes heading, magnetic latitude, or rolls, the
A-coil strength must be changed accordingly.
Automatic degaussing (AUTODEG) control
equipment adjusts some or all of the coil currents
automatically with changes in ship's attitude (heading,
roll, pitch, trim, and list) or with changes in both attitude
and location. AUTODEG control equipment is installed
on all ships with degaussing coils installed in more
than one place. Currently, the two basic types of
Figure 10-11.--A coil.
AUTODEG control equipment currently are