eBook: Automating Manufacturing Systems; with PLCs


A.22 V

Vac - a voltage that is AC.
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 flow and appear to be shed.

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