INFORMATION EXCHANGE AND
converts the sensed discrete or analog output signal into
PROCESSING METHODS
various forms used throughout the PCS.
DISCRETE SIGNAL CONDITIONER.-- T h e
In this section, we will describe the methods used
discrete signal conditioner converts its sensed signal to
by the control consoles to communicate between each
an output signal level of 0 to +5 volts dc (logic 0 or 1).
other and between the engineering plant equipments and
This signal is used to light the front panel indicator and
the consoles. We will discuss the various types of
trigger an alarm generation circuit. Often the sensed
sensory devices used, signal conditioning, and data
signal is conditioned to an output level of 0 or 3.5 volts
processing and distribution. Our discussion also will
dc (logic 0 or 1) to be compatible with the PCS.
include a brief description of the processor program.
ANALOG SIGNAL CONDITIONER.-- T h e
analog signal conditioner converts its input sensed
Sensors and Remote Signal Conditioning
signal to a 0- to 10-volt continuous output analog signal.
T h e s e input signals are from fuel tank level,
Most of the information the engineering plant
temperature, turbine speed, and pressure sensors.
control system receives is developed from various
sensors located throughout the engineering plant. A
Processor Hardware
sensor is a device that responds to a physical stimulus
and sends a resulting signal. The physical stimulus can
All digital computers (processors) are divided into
be a fluid level, air pressure, motor speed, switch or relay
the following four basic units:
contact closure, or exhaust temperature. The resulting
output from the sensor is an electrical signal.
1. Control
Sensors are referred to by many names, depending
2. Arithmetic
u p o n the manufacturer, construction, or use. For
3. Memory
example, they might be called a detector, transducer, or
shaft encoder.
4. I/O
The engineering plant control system uses many
Using these four units with data lines, address lines,
types of sensors to detect different parameter inputs, and
and control lines, the computer can effectively respond
it changes this input to an electrical signal. The types of
to the demands and protection of the engineering plant
sensors used on the FFG-7 class ships include the
systems under a preprogrammed set of instructions.
following:
Let's briefly look at each of these units.
1 . Tank fluid level
CONTROL UNIT.-- A set of cards in the processor
makes up the control unit. This set of cards provides the
2 . Temperature sensors
control logic that enables the computer to execute the
3. Pressure sensors
desired instructions and control the address generation.
These cards also control the timing required to execute
4. Tachometer sensors
power-up initialization and processor control.
5. Contact closure
ARITHMETIC UNIT.-- The set of cards that
6. Vibration sensors
makes up the arithmetic unit performs all the arithmetic
The propulsion control system (PCS) uses two types
functions for the processor, such as address offset and
of sensed output signals: (1) conditioned and (2)
jump computation. In reality, the only true arithmetic
unconditioned. These signals drive the light indicators,
function performed by this unit is adding two numbers.
meters, motors, and alarms. The interface circuitry
The unit uses the most significant bit (bit 0) to indicate
p e r f o r m s various functions. These functions are
the sign of arithmetic values and the negative number to
p e r f o r m e d by analog-to-digital (A/D) converters,
be represented in the two's complement to perform
multiplexer, alarm and tone generators, relay and lamp
subtraction by addition.
drivers, and processors.
MEMORY UNIT.-- The memory section of the
Both discrete
and analog sensed signals may be
processor includes read only memory (ROM) and
signal conditioned
or unconditioned. The unconditioned
random access memory (RAM). Addressing the ROM
sensed signal goes
directly to the equipment item it is
and RAM boards is accomplished by memory address
driving: a lamp
or a meter. The signal conditioner
multiplexer in the processor. The ROM contains both
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