Introduction
Page 5 of 31
Doc No.: MAN01502, 27-02-01 SCA 300 Manual
the simplicity of the non follow-up system by having the jog lever directly
operate the directional solenoid valve. Since the jog lever is a non follow-
up input device directly operating the directional solenoids, it does not
provide proportional control of the steering gear. Operating the jog lever
to port or starboard will immediately apply a fixed amount of current to the
directional valve solenoids. The fixed amount of current applied under
non follow-up operation, and therefore the fixed speed the steering gear
can achieve under non follow-up operation, is adjustable through a current
limiting, adjustable wire wound resistor in the SCA 300.
If a jog lever is to be used with the SCA a non follow-up/full follow-up
(NFU/FFU) switch will be required to select between these two types of
operation. A further "dodge" function can be accommodated with certain
jog levers. Refer to the jog lever manual for various options.
WARNING: IN ORDER TO AVOID POSSIBLE STEERING GEAR DAMAGE,
EXTERNAL LIMIT SWITCHES MUST BE USED WITH A JOG LEVER.
Autopilots can also be connected to the SCA as either a full follow-up
input device generating a rudder order signal or similar to a non follow-up
jog lever controlling the solenoid directly. Contact your Jastram
representative for further information on connecting autopilots to the SCA
300.
Rudder Feedback Unit
The rudder feedback unit (RFU) is mechanically tied to the ship's rudder
and converts the position of the rudder into an electronic signal. This
signal is called the rudder angle signal. The SCA is designed to be used
with the RFU 1300 but other types of rudder feedback units may be used.
Contact your Jastram representative for further information on connecting
other feedback units to the SCA.
Jastram's RFU 1300 operates in "stand alone” mode. This ensures that
all electronic circuitry necessary to drive the rudder angle indicators is
contained within the RFU 1300. This circuitry is simple and separating it
ensures constant rudder angle indication regardless of the status of the
amplifier unit. The RFU 1300 also contains limit switches which cut the
electric signals to the directional solenoid valve at the rudder's hard over
positions. This limits the travel of the steering gear to prevent possible
damage (see Figure 2).
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