18WuD2x

318 graphic recorder • gray tin
graphic recorder An instrument in which a signaldriven
pen or stylus makes a permanent record of
a quantity on graph paper. The paper passes at a
controlled speed beneath the pen.
graphics
1. Diagrams, charts, photos, tables, or
similar, often symbolic, artwork used to convey
information. 2. The video display in a computer
system. 3. Computer software designed specifically
to create and edit illustrations.
graphic solution 1. A method of depicting the solution(s)
to a problem or equation by means of
graphs. 2. The process of solving problems or
equations with the aid of graphs.
graphic terminal A display or plotter that provides
visual output of a computer run.
graphite A soft form of carbon used in resistors,
attenuators, contacts, brushes, vacuum-tube
plates, cathode-ray tube coatings, etc.
graphite-line resistor An emergency, makeshift
resistor consisting of a pencil line drawn on a
piece of paper. The heavier the line for a given
width and length, the lower its resistance.
graphophone Archaic term for phonograph.
grasping planning A scheme that a robot arm and
gripper use to get hold of a particular object. It
can use a vision system, a bar-code reader, tactile
sensing, and/or proximity sensing. The robot
controller (computer) must be programmed to
recognize the input from these devices, and to
seek out the object.
grass The background noise (noise floor) on the
display of a spectrum analyzer; it also appears on
certain types of radar displays.
grasshopper fuse A special type of spring-operated
fuse. When it burns out, it actuates an alarm that
alerts personnel of a possible circuit or system
malfunction.
graticule Calibrated gridwork, as on the face of an
oscilloscope or spectrum-analyzer screen.
grating A set of parallel, closely spaced, equidistant
conductors or bars. When an electromagnetic
field that has a wavelength comparable to
the conductor spacing passes through the plane
containing the conductors, diffraction occurs,
producing an interference pattern. An adaptation
of this device, called a DIFFRACTION GRATING,
is used to separate visible light into its constituent
spectral colors.
grating reflector A metal antenna reflector consisting
of numerous parallel, straight, closely
spaced conductors. When the conductor spacing
is much smaller than the wavelength, the set behaves
like a solid sheet of metal.
Gratz rectifier A form of full-wave rectifier circuit
in a three-phase, alternating-current system.
gravitational constant Symbol, g. The acceleration
produced by the attraction of a unit mass at
unit distance; g = 6.673 × 10 –11 N•m 2 /kg 2 .
gravitational wave See GRAVITY WAVE.
gravity 1. The universal force of attraction between
material bodies—especially that force evidenced
by the earth’s drawing of bodies toward its center,
causing them to have weight. 2. Abbreviation, g.
The rate at which a free-falling mass accelerates
in a vacuum at the earth’s surface; equal to 9.802
meters per second per second (m/s 2 ). 3. The rate
at which a free-falling mass accelerates in a vacuum
in the vicinity, or at the surface, of an astronomical
object, such as a planet or star.
gravity cell An electrochemical cell in which the
positive electrode is made of copper and the negative
electrode is made of zinc. The copper electrode
is placed at the bottom of a jar, and the zinc
electrode is placed at the top. The jar is half filled
with copper sulfate solution, and then filled with
zinc sulfate solution. The solutions remain separate
because copper sulfate has a higher specific
gravity than zinc sulfate.
gravity wave A disturbance in a gravitational field,
such as might be caused by a collapsing star.
These waves might emanate from black holes or
rapidly spinning neutron stars.
gray body A radiating body exhibiting constant
spectral emissivity at all wavelengths. That is, the
emitted energy is the same at all wavelengths and
all frequencies.
Gray code A computer code in which the expressions
representing sequential numbers differ in
only one bit.
gray scale A reference scale for use in black-andwhite
television and video display images, consisting
of several defined levels of brightness with
neutral color.
Gray scale:
hypothetical 16-shade binary codes.
Percent
Code Relative shade brightness
0000 Black 0.00
0001 6.67
0010 Very dark gray 13.33
0011 20.00
0100 Dark gray 26.67
0101 33.33
0110 Medium-dark gray 40.00
0111 46.67
1000 Medium gray 53.33
1001 60.00
1010 Medium-light gray 66.67
1011 73.33
1100 Light gray 80.00
1101 86.67
1110 Off-white 93.33
1111 White 100.00
gray tin A form of tin that exhibits some properties
of a semiconductor at temperatures below 18 degrees
Celsius.