Cut Sheet
Volume 8—Sensing Solutions CA08100010E—November 2012 www.eaton.com V8-A2-5
Appendix 2
Glossary of Terms
Electromechanical Limit
Switch—A pilot control
device that converts a
mechanical motion via
physical contact with a target
into an electrical control
signal. The rotary arm or push
rod on the switch body
housing is mechanically
connected to the switching
element inside. The cam,
machine component or
moving object comes into
contact with the limit switch
at a pre-determined position.
Embedded—A shielded
core/coil sensor “embedded”
in the surrounding metal
mounting. The sensor
operation is not affected by
surrounding metal. Also
referred to as “Flush
Mounting.”
Emitter—See
Thru-Beam
Source
.
Enclosed Switch—A basic
switch unit enclosed in a
metal housing to provide
increased durability and
conduit connection.
Excess Gain—Measurement
of the sensing power of a
photoelectric sensor to
detect an object in a given
environment.
External Mounting
Enclosure—Enclosure
mounting provisions external
to the apparatus cavity.
Fahrenheit/Celsius—
Temperature scale
conversion.
F° = 9/5 (C°) +32
C° = 5/9 (F°) –32
Ferrous—Metallic material
which contains steel, nickel
or cobalt.
Fiber Optic—Sensor with
remote optics comprised of
thin plastic or glass fibers, for
detection in very tight places
or extremely harsh
environments.
Field of View—The region
illuminated by the light
source and seen by the
detector. Field of View is
sometimes referred to as
“spot size” and may be
expressed as a circle
diameter at a given range, or
in degrees emanating from
the sensor. In both cases,
Field of View is a three-
dimensional area roughly the
shape of a cone.
Fixed Focus—A sensing
mode where the light source
and the detector are angled
towards one another, forming
a focal point. The target will
only be detected in this area
where the source and
detector fields of view cross.
Flush Mounting
Enclosure—So designed as
to have a minimal front
projection when set into and
secured to a flat surface.
Free Position (F.P.)—
Position of switch plunger or
actuator when no external
force is applied other than
gravity.
Hysteresis—The difference
between the sensor operate
point, where the target is
detected, and release point,
where the target is no longer
detected.
IEC—International
Electrotechnical Commission.
Writes recommended
performance and safety
standards for electrical
products.
Inductive Proximity
Sensor—A non-contact
proximity sensor that
operates on the principle of
induced electromagnetic field
(for example, eddy currents)
in the surface of a metallic
target. It detects the
presence or absence of a
metal object without physical
contact. It is a self-contained,
solid-state device with no
moving parts.
Infrared—Invisible light
radiation at wavelengths of
690 nanometers and longer.
Lateral Approach—(Side-By)
Approach path of a target
perpendicular to the
reference axis, target
approaches the sensor from
the si
de.
Leakage Current—S
mall
current flowing through a
sol
id-state output when in the
OFF state.
LED (Light Emitting
Diode)—Semi-conductor that
generates monochromatic
light when current flows in
the conductive direction.
Shock/vibration resistant,
long life, low current draw
alternative to incandescent
lamps. As a low power, no
heat source of light, the LED
is the standard light source
for photoelectric sensors.
LED Indicators—Light
emitting diodes (LEDs)
provide diagnostic
information as to the status
of the sensor (operated or not
operated). Diagnostic
indications are switch status,
power ON/OFF status and/or
short circuit conditions.
Light Curtain—Specialized
reflex sensor head that emits
a fan-shaped beam of light.
Light Operate—A light
operate sensor generates an
output when the source light
intensity is sufficiently
increased at the detector (the
sensor sees “light”).
Line-Powered Sensor—
(Three-wire) A sensor that
draws its operating current
(burden current) directly from
the line. Its operating current
does not flow through the
load. Three connections are
required.
Load-Powered Sensor—
(Two-wire) A sensor that
draws its operating current
(residual current) through the
load. Load Powered Sensors
require only two connections
(exclusive of ground) and are
always in series with the
load.
Load Release Time—The
time delay which occurs
between the point at which
the sensor output restores to
the not operated state and
the load restores to OFF-
state condition.
Maintained Contact—
Sustained contact after
plunger has been released,
but can be reset.
Make—To close or establish
a path for electrical current.
Minimum Holding
Current—Current required to
sustain a solid-state sensor in
an operating condition.
Modulated Light Sensors—
A photoelectric sensor that
operates on light pulses
rather than on constant light
intensity.
Momentary Contact—
Contacts return from
operated position to normal
condition when actuating
force is removed.
Nanometer (nm)—This is
the typical unit of measure for
the wavelength of source
light in a photoelectric
sensor.
1 Nano-meter is equal to 10
-9
meter.
NEMA—National Electrical
Manufacturers Association,
United States.
Non-embeddable—An
inductive style that requires a
generous metal-free area
surrounding the sensor face
to allow for the longest
sensing distances, often four
times the shielded range.
Non-ferrous—Metallic
material which does not
contain steel, nickel or cobalt.
Example: Aluminum