Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.29
operating system is very well debugged.
UPS (Uninterruptable Power Supply) -
user friendly - a design scheme that similifies interaction so that no knowledge is needed to operae a device
and errors are easy to recover from. It is also a marketing term that is badly misused.
user interfaces - are the means of communicating with the computer. For CAD applications, a graphical
interface is usually preferred. User friendliness is a measure of the ease of use of a program and
implies a good user interface.
UUCP (Unix to Unix Copy Program) - a common communication method between UNIX systems.
35.22 V
Vac-avoltagethatisAC.
vacuum - a pressure that is below another pressure.
vane - a blade that can be extended to provide a good mechanical contact and/or seal.
variable - a changeable location in memory.
varistor - voltage applied changes resistance.
valve - a system component for opening and closing mass/energy flow paths. An example is a water faucet
or transistor.
vapor - a gas.
variable - it is typically a value that will change or can be changed. see also constant.
VDT (Video Display Terminal) - also known as a dumb terminal
velocity - a rate of change or speed.
Venturi - an effect that uses an orifice in a flow to generate a differential pressure. These devices can
generate small vacuums.
viscosity - when moved a fluid will have some resistance proportional to internal friction. This determines
how fast a liquid will flow.
viscosity index - when heated fluid viscosity will decrease, this number is the relative rate of change with
respect to temperature.
VLSI (Very Large Scale Integration) - a measure of chip density. This indicates that there are over
100,000(?) transistors on a single integrated circuit. Modern microprocessors commonly have
millions of transistors.
volt - a unit of electrical potential.
voltage rating - the range or a maximum/minimum limit that is required to prevent damage, and ensure
normal operation. Some devices will work outside these ranges, but not all will, so the limits
should be observed for good designs.
volume - the size of a region of space or quantity of fluid.
volatile memory - most memory will lose its contents when power is removed, making it volatile.
vortex - a swirling pattern in fluid flow.
vortex shedding - a solid object in a flow stream might cause vortices. These vortices will travel with the
flowandappeartobeshed.
35.23 W
watchdog timer - a timer that expects to receive a pulse every fraction of a second. If a pulse is not received,
it assumes the system is not operating normally, and a shutdown procedure is activated.
watt - a unit of power that is commonly used for electrical systems, but applies to all.
wavelength - the physical distance occupied by one cycle of a wave in a propagating medium.
word - 1. a unit of 16 bits or two bytes. 2. a term used to describe a binary number in a computer (not limited