Industrial Automation Glossary – N, O, P
Written by Neal Babcock
NAK (Negative AKnowledgement)
an ASCII control code.
NAMUR
A European standards organization.
NAND (Not AND)
a Boolean AND operation with the result inverted.
narrowband
uses a small data transmission rate to reduce spectral requirements.
NC
see normally opened/closed
NC (Numerical Control)
a method for controlling machine tools, such as mills, using simple programs.
negative logic
a 0 is a high voltage, and 1 is a low voltage. In Boolean terms it is a duality.
NEMA (National Electrical Manufacturers Association)
this group publishes numerous standards for electrical equipment.
nephelometry
a technique for determining the amount of solids suspended in water using light.
nesting
a term that describes loops
network
a connection of typically more than two computers so that data, email, messages, resources and files may be shared.
NFS (Network File System)
a protocol developed by Sun Microsystems to allow dissimilar computers to share files. The effect is that the various mounted remote disk drives act as a single local disk.
NIC (Network Interface Card)
a computer card that allows a computer to communicate on a network, such as ethernet.
NIST (National Institute of Standards and Technology)
formerly NBS.
NO
see normally open
node
one computer connected to a network.
noise
1. electrical noise is generated mainly by magnetic fields (also electric fields) that induce currents and voltages in other conductors, thereby decreasing the signals present. 2. a sound of high intensity that can be perceived by the human ear.
non
fatal error
non-positive displacement pump
a pump that does not displace a fixed volume of fluid or gas.
non-retentive
when power is lost values will be set back to 0.
NOR (Not OR)
a Boolean function OR that has the results negated.
normally opened/closed
refers to switch types. when in their normal states (not actuated) the normally open (NO) switch will not conduct current. When not actuated the normally closed (NC) switch will conduct current.
NOT
a Boolean function that inverts values. A 1 will become a 0, and a 0 will become a 1.
NOVRAM (NOn Volatile Random Access Memory)
memory that does not lose its contents when turned off.
NPN
a bipolar junction transistor type. When referring to switching, these can be used to sink current to ground.
NPSM
American national standard straight pipe thread for mechanical parts.
NPT
American national standard taper pipe thread.
NSF (National Science Foundation)
a large funder of science projects in USA.
NSFNET (National Science Foundation NETwork)
funded a large network(s) in USA, including a high speed backbone, and connection to a number of super computers.
NTSC (National Television Standards Committee)
a Red
null modem
a cable that connects two RS
OCR (Optical Character Recognition)
Images of text are scanned in, and the computer will try to interpret it, much as a human who is reading a page would. These systems are not perfect, and often rely on spell checkers, and other tricks to achieve reliabilities up to 99%
octal
a base 8 numbering system that uses the digits 0 to 7.
Octave
a doubling of frequency
odd parity
a bit is set during communication to indicate when the data should have an odd number of bits.
OEM (Original Equipment Manufacturer)
a term for a manufacturer that builds equipment for consumers, but uses major components from other manufacturers.
off
line
offset
a value is shifted away or towards some target value.
on
line
one
shot
opcode (operation code)
a single computer instruction. Typically followed by one or more operands.
open
system
open collector
this refers to using transistors for current sourcing or sicking.
open loop
a system that does monitor the result. open loop control systems are common when the process is well behaved.
operand
an operation has an argument (operand) with the mnemonic command.
operating system
software that existing on a computer to allow a user to load/execute/develop their own programs, to interact with peripherals, etc. Good examples of this is UNIX, MS
optimization
occurs after synthesis and after a satisfactory design is created. The design is optimized by iteratively proposing a design and using calculated design criteria to propose a better design.
optoisolators
devices that use a light emitter to control a photoswitch. The effect is that inputs and outputs are electrically separate, but connected. These are of particular interest when an interface between very noisy environments are required.
OR
the Boolean OR function.
orifice
a small hole. Typically this is places in a fluid/gas flow to create a pressure difference and slow the flow. It will increase the flow resistance in the system.
oscillator
a device that produces a sinusoidal output.
oscilloscope
a device that can read and display voltages as a function for time.
OSHA (Occupational safety and Health Act)
these direct what is safe in industrial and commercial operations.
OSI (Open System Interconnect)
an international standards program to promote computer connectivity, regardless of computer type, or manufacturer.
overflow
the result of a mathematical operation passes by the numerical limitations of the hardware logic, or algorithm.
overshoot
the inertia of a controlled system will cause it to pass a target value and then return.
parallel communication
bits are passed in parallel conductors, thus increasing the transmission rates dramatically.
parallel design process
evaluates all aspects of the design simultaneously in each iteration. The design itself is sent to all analysis modules including manufacturability, and engineering analysis modules; redesign decisions are based on all results at once.
parallel programs
theoretically, these computer programs do more than one thing simultaneously.
parity
a parity bit is often added to bytes for error detection purposes. The two typical parity methods are even and odd. Even parity bits are set when an even number of bits are present in the transmitted data (often 1 byte = 8 bits).
particle velocity
the instantaneous velocity of a single molecule.
Pascal
a basic unit of pressure
Pascal’s law
any force applied to a fluid will be transmitted through the fluid and act on all enclosing surfaces.
PCB (Printed Circuit Board)
alternate layers of insulating materials, with wire layout patterns are built up
peak
to
peak level
the maximum pressure level for a cyclic variation
peer
to
performance variables
are parameters which define the operation of the part. Performance variables are used by the designer to measure whether the part will perform satisfactorily.
period
the time for a repeating pattern to go from beginning to end.
peripheral
devices added to computers for additional I/O.
permanent magnet
a magnet that retains a magnetic field when the original magnetizing force is removed.
petri
net
pH
a scale for determining is a solution is an acid or a base. 0
photocell
a device that will convert photons to electrical energy.
photoconductive cell
a device that has a resistance that will change as the number of incident photons changes.
photoelectric cell
a device that will convert photons to electrical energy.
photon
a single unit of light. Light is electromagnetic energy emitted as an electron orbit decays.
physical layer
an OSI network model layer.
PID (Proportional Integral Derivative)
a linear feedback control scheme that has gained popularity because of its relative simplicity.
piezoelectric
a material (crystals/ceramics) that will generate a charge when a force is applied. A common transducer material.
ping
an internet utility that makes a simple connection to a remote machine to see if it is reachable, and if it is operating.
pink noise
noise that has the same amount of energy for each octave.
piston
it will move inside a cylinder to convert a pressure to a mechanical motion or vice versa.
pitch
a perceptual term for describing frequency. Low pitch means low frequency, high pitch means a higher frequency.
pitot tube
a tube that is placed in a flow stream to measure flow pressure.
pixels
are picture elements in a digitally generated and displayed picture. A pixel is the smallest addressable dot on the display device.
PLA (Programmable Logic Array)
an integrated circuit that can be programmed to perform different logic functions.
plane sound wave
the sound wave lies on a plane, not on a sphere.
PLC (Programmable Logic Controller)
A rugged computer designs for control on the factory floor.
pneumatics
a technique for control and actuation that uses air or gases.
PNP
a bipolar junction transistor type. When referring to switching, these can be used to source current from a voltage source.
poise
a unit of dynamic viscosity.
polling
various inputs are checked in sequence for waiting inputs.
port
1. an undedicated connector that peripherals may be connected to. 2. a definable connection number for a machine, or a predefined value.
positive displacement pump
a pump that displaces a fixed volume of fluid.
positive logic
the normal method for logic implementation where 1 is a high voltage, and 0 is a low voltage.
potentiometer
displacement or rotation is measured by a change in resistance.
potting
a process where an area is filled with a material to seal it. An example is a sensor that is filled with epoxy to protect it from humidity.
power level
the power of a sound, relative to a reference level
power rating
this is generally the maximum power that a device can supply, or that it will require. Never exceed these values, as they may result in damaged equipment, fires, etc.
power supply
a device that converts power to a usable form. A typical type uses 115Vac and outputs a DC voltage to be used by circuitry.
PPP (Point
to
presentation layer
an OSI network model layer.
pressure
a force that is distributed over some area. This can be applied to solids and gases.
pressure based flow meter
uses difference in fluid pressures to measure speeds.
pressure switch
activated above/below a preset pressure level.
prioritized control
control operations are chosen on the basic of priorities.
procedural language
a computer language where instructions happen one after the other in a clear sequence.
process
a purposeful set of steps for some purpose. In engineering a process is often a machine, but not necessarily.
processor
a loose term for the CPU.
program
a sequential set of computer instructions designed to perform some task.
programmable controller
another name for a PLC, it can also refer to a dedicated controller that uses a custom programming language.
protocol
conventions for communication to ensure compatibility between separated computers.
proximity sensor
a sensor that will detect the presence of a mass nearby without contact. These use a variety of physical techniques including capacitance and inductance.
pull
up resistor
pulse
a brief change in a digital signal.
purge bubbling
a test to determine the pressure needed to force a gas into a liquid.
PVC
poly vinyl chloride
pyrometer
a device for measuring temperature
