Industrial Automation Glossary – G, H, I

galvanometer
a simple device used to measure currents. This device is similar to a simple DC motor.

gamma rays
high energy electromagnetic waves resulting from atomic fission or fusion.

gate
1. a circuit that performs on of the Boolean algebra function (i.e., and, or, not, etc.) 2. a connection between a runner and a part, this can be seen on most injection molded parts as a small bump where the material entered the main mold cavity.

gateway
translates and routes packets between dissimilar networks.

Geiger
Mueller tube

global optimum
the absolute best solution to a problem. When found mathematically, the maximum or minimum cost/utility has been obtained.

gpm (gallons per minute)
a flow rate.

grafcet
a method for programming PLCs that is based on Petri nets. This is now known as SFCs and is part of the IEC 1131

gray code
a modified binary code used for noisy environments. It is devised to only have one bit change at any time. Errors then become extremely obvious when counting up or down.

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.

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)

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.

horsepower
a unit for measuring power

host
a networked (fully functional) computer.

hot backup
a system on

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 re-polarization in a reversing field, and in friction this is an effect based on coulomb friction that reverses sticking force.

Hz
see hertz

I/O (Input/Output)
a term describing anything that goes into or out of a computer.

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)

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 function.

impedance
In electrical systems this is both reactive and real resistance combined. This also applies to power transmission and flows in other types of systems.

impulse Noise
a short duration, high intensity noise. This type of noise is often associated with explosions.

increment
increase a numeric value.

inductance
current flowing through a coil will store energy in a magnetic field.

inductive heating
a metal part is placed inside a coil. A high frequency AC signal is passed through the coil and the resulting magnetic field melts the metal.

inertia
a property where stored energy will keep something in motion unless there is energy added or released.

inference
to make a decision using indirect logic. For example if you are wearing shoes, we can infer that you had to put them on. Deduction is the complementary concept.

inference engine
the part of an expert system that processes rules and facts using forward or backward chaining.

infrared
light that has a frequency below the visible spectrum.

instruction set
a list of all of the commands that available in a programmable system. This could be a list of PLC programming mnemonics, or a list of all of the commands in BASIC.

instrument
a device that will read values from external sensors or probes, and might make control decision.

integral control
a control method that looks at the system error over a long period of time. These controllers are relatively immune to noise and reduce the steady state error, but the do not respond quickly.

integrate
to combine two components with clearly separable functions to obtain a new single component capable of more complex functions.

intelligence
systems will often be able to do simple reasoning or adapt. This can mimic some aspects of human intelligence. These techniques are known as artificial intelligence.

intelligent device
a device that contains some ability to control itself. This reduces the number of tasks that a main computer must perform. This is a form of distributed system.

interface
a connection between a computer and another electrical device, or the real world.

interlock
a device that will inhibit system operation until certain conditions are met. These are often required for safety on industrial equipment to protect workers.

interlock
a flag that ensures that concurrent streams of execution do not conflict, or that they cooperate.

intermittent noise
when sounds change level fluctuate significantly over a measurement time period.

interpreter
programs that are not converted to machine language, but slowly examined one instruction at a time as they are executed.

interrupt
a computer mechanism for temporarily stopping a program, and running another.

inverter
a logic gate that will reverse logic levels from TRUE to/from FALSE.

ion
an atom, molecule or subatomic particle that has a positive or negative charge.

IOR (Inclusive OR)
a normal OR that will be true when any of the inputs are true in any combinations. also see Exclusive OR (EOR).

IP (internet Protocol)
the network layer (OSI model) definitions that allow internet use.

IP datagram
a standard unit of information on the internet.

ISDN (Integrated Services Digital Network)
a combined protocol to carry voice, data and video over 56KB lines.

ISO (International Standards Organization)
a group that develops international standards in a wide variety of areas.

isolation
electrically isolated systems have no direct connection between two halves of the isolating device. Sound isolation uses barriers to physically separate rooms.

isolation transformer
a transformer for isolating AC systems to reduce electrical noise.