Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.21
OSF (Open Software Foundation) - a consortium of large corporations (IBM, DEC, HP) that are promoting
DCE. They have put forth a number of popular standards, such as the Motif Widget set for X-
Windows programming.
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.
overshoot - the inertia of a controlled system will cause it to pass a target value and then return.
overflow - the result of a mathematical operation passes by the numerical limitations of the hardware logic,
or algorithm.
35.16 P
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, inspectibility, 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-abasicunitofpressure
Pascal’s law - any force applied to a fluid will be transmitted through the fluid and act on all enclosing
surfaces.
PC (Programmable Controller) - also called PLC.
PCB (Printed Circuit Board) - alternate layers of insulating materials, with wire layout patterns are built up
(sometimes with several layers). Holes thought the layers are used to connect the conductors to
each other, and components inserted into the boards and soldered in place.
PDES (Product Data Exchange using Step) - a new product design method that has attempted to include all
needed information for all stages of a products life, including full solids modeling, tolerances, etc.
peak level - the maximum pressure level for a cyclic variation
peak-to-peak - the distance between the top and bottom of a sinusoidal variation.
peer-to-peer - a communications form where connected devices to both read and write messages at any time.
This is opposed to a master slave arrangement.
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 - an enhanced state space diagram that allows concurrent execution flows.
pH - a scale for determining is a solution is an acid or a base. 0-7 is acid, 7-4 is a base.
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 it’s relative simplicity.