Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.14
ground - a buried conductor that acts to pull system neutral voltage values to a safe and common level. All
electrical equipment should be connected to ground for safety purposes.
GUI (Graphical User Interface) - the user interacts with a program through a graphical display, often using a
mouse. This technology replaces the older systems that use menus to allow the user to select
actions.
35.8 H
half cell - a probe that will generate a voltage proportional to the hydrogen content in a solution.
half duplex - see HDX
handshake - electrical lines used to establish and control communications.
hard copy - a paper based printout.
hardware - a mechanical or electrical system. The ‘functionality’ is ‘frozen’ in hardware, and often difficult
to change.
HDLC (High-level Data Link Control) - an ISO standard for communications.
HDX (Half Duplex) - a two way serial connection between two computer. Unlike FDX, characters that are
sent are not reflected back to the sender.
head - pressure in a liquid that is the result of gravity.
hermetic seal - an airtight seal.
hertz - a measure of frequency in cycles per second. The unit is Hz.
hex - see hexadecimal.
hexadecimal - a base 16 number system where the digits are 0 to 9 then A to F, to give a total of 16 digits.
This is commonly used when providing numbers to computers.
high - another term used to describe a Boolean true, logical positive, or one.
high level language - a language that uses very powerful commands to increase programming productivity.
These days almost all applications use some form of high level language (i.e., basic, fortran,
pascal, C, C++, etc.).
horsepower - a unit for measuring power
host - a networked (fully functional) computer.
hot backup - a system on-line that can quickly replace a failed system.
hydraulic - 1. a study of water 2. systems that use fluids to transmit power.
hydrocarbon - a class of molecules that contain carbon and hydrogen. Examples are propane, octane.
hysteresis - a sticking or lagging phenomenon that occurs in many systems. For example, in magnetic
systems this is a small amount of magnetic repolarization in a reversing field, and in friction this
is an effect based on coulomb friction that reverses sticking force.
Hz - see hertz
35.9 I
IAB (internet Activities Board) - the developer of internet standards.
IC (Integrated Circuit) - a microscopic circuit placed on a thin wafer of semiconductor.
IEC (International Electrical Commission) - A Swiss electrical standards group.
IEEE (Institute of Electrical and Electronics Engineers) -
IEEE802 - a set of standards for LANs and MANs.
IGES (Initial Graphics Exchange Specification) - a standard for moving data between various CAD systems.
In particular the format can handle basic geometric entities, such as NURBS, but it is expected to
be replaced by PDES/STEP in the near future.
impact instrument - measurements are made based by striking an object. This generally creates an impulse
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