Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.19
etc.
module - a part o a larger system that can be interchanged with others.
monitor - an operation mode where the compuer can be watched in detail from step to step. This can also
refer to a computer screen.
motion detect flow meter - a fluid flow induces measurement.
MRP (Material Requirements Planning) - a method for matching material required by jobs, to the equipment
available in the factory.
MSD (Most Significant Digit) - the larget valued digit in a number (eg. 6 is the MSD in 63422). This is often
used for binary numbers.
MTBF (Mean Time Between Failure) - the average time (hours usually) between the last repair of a product,
and the next expected failure.
MTTR (Mean Time To Repair) - The average time that a device will out of use after failure before it is
repaired. This is related to the MTBF.
multicast - a broadcast to some, but not necessarily all, hosts on a network.
multiplexing - a way to efficiently use transmission media by having many signals run through one
conductor, or one signal split to run through multiple conductors and rejoined at the receiving
end.
multiprocessor - a computer or system that uses more than one computer. Normally this term means a single
computer with more than one CPU. This scheme can be used to increase processing speed, or
increase reliability.
multivibrator - a digital oscillator producing square or rectangular waveforms.
35.14 N
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 (such as FOR-NEXT loops) within loops in programs.
network - a connection of typically more than two computers so that data, email, messages, resources and
files may be shared. The term network implies, software, hardware, wires, etc.
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 Interace Card) - a computer card that allows a computer to communicate on a network, such
as ethernet.
NIH (Not Invented Here) - a short-lived and expensive corporate philosophy in which employees believe
that if idea or technology was not developed in-house, it is somehow inferior.
NIST (National Institute of Standards and Technology) - formerly NBS.
NO - see normally opened
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 - a minor error that might indicate a problem, but it does not seriously interfere with the
program execution.
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