Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.22
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-Point Protocol) - allows router to router or host to network connections over other
synchronous and asynchronous connections. For example a modem connection can be used to
connect to the internet using PPP.
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.
PROM (Programmable Read Only Memory) -
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 - this is used to normally pull a voltage on a line to a positive value. A switch/circuit can be