Cut Sheet

V8-A2-4 Volume 8—Sensing Solutions CA08100010E—November 2012 www.eaton.com
Appendix 2
Glossary of Terms
Glossary of Terms
Acid-Resistant Enclosure—
So constructed that it will not
be injured readily by exposure
to acid fumes.
Actuator—Mechanism of
the limit switch that operates
the contacts.
Alignment—Positioning of
light source and detector,
reflector or target in order to
obtain maximum signal
strength (see also
Excess
Gain
).
Ambient Light—Light
reaching a sensor detector
that is not generated by its
light source.
Amp or Ampere—A unit of
measurement of electric
current produced by one volt
acting through the resistance
of one ohm.
Axial Approach—(Head-On)
The target approaches the
sensing face of the sensor
with its center moving along
the reference axis of the coil/
core. The target surface is
parallel to the sensor face.
Bend Radius—The minimum
radius that a fiber optic cable
can withstand without
breaking the fibers.
Break—To open an electrical
circuit.
Break Distance—The
effective open gap distance
between the stationary and
movable objects.
Burden Current—The
operating current of a line
powered, three-wire, solid-
state sensor. This current
does not pass through the
load.
Cam—Machine part or
component that applies force
to the switch actuator,
causing it to move as
intended.
Capacitance—The ability of
insulators to store an
electrical charge.
Capacitive Proximity
Sensor—A sensor that
operates on the principle of
dielectric capacitance with a
target. It detects the
presence or absence of
metallic or nonmetallic
objects without physical
contact. It is a self-contained,
solid-state device with no
moving parts. Sensitivity
adjustment provided.
Celsius—See
Fahrenheit/
Celsius
.
CENELEC—European
Committee for Electro-
Technical Standardization.
Complementary Output—
Sensors with normally open
(NO) and normally closed
(NC) outputs, both of which
change state simultaneously.
Contrast—The ratio between
excess gain under light
conditions and excess gain
under dark conditions. The
higher the contrast ratio, the
higher the reliability of the
sensing application.
CSA
®
—Canadian Standards
Association, Canada.
Current—The rate of flow of
electric charge in an electrical
circuit.
Current Sinking Sensor
(NPN) or N Type—The
negative terminal of a DC
system is called the sink,
because conventional current
normally flows into it. A
current sinking sensor
“sinks” the current from the
load.
Current Sourcing Sensor
(PNP) or P Type—The
positive terminal of a DC
system is called the source,
because conventional current
normally flows from it. A
current sourcing sensor
“sources” the current to the
load.
Damping—A loading effect
due to eddy currents being
induced into the surface of a
sensed metallic target,
causing a reduction in
amplitude of the inductive
proximity sensor’s oscillator
signal.
Dark Operate—A dark
operate sensor generates an
output when the source light
intensity is sufficiently
reduced at the detector (the
sensor sees “dark”).
Detector—See
Thru-Beam
Detector
.
Dielectric—The insulator
separating the plates in a
capacitor.
Differential or Differential
Travel (D.T.)—Plunger or
actuator travel from point
where contacts “snap over”
to point where they “snap
back.”
Diffuse Reflective
Sensing—A photoelectric
sensing method in which the
light from the source hits the
target surface and is then
diffused from the surface in
all directions. Part of this light
returns to the detector. If the
intensity is high enough, the
sensor generates an output.
This is sometimes referred to
as photoelectric “proximity”
sensing.
DIN—Deutsch Industrie
Norm, Federal Republic of
Germany (dimensions).
Double Break Contacts—
Circuit “breaks” in two
places.
Double Insulated
Enclosure—
An insulation
system with the two
insulations physically
separated and so arranged
that they are not
simultaneously subjected to
the same deteriorating
influences (temperature,
contaminants, and so on) to
the same degree.
Double Pole, Double Throw
(DPDT)—A switch that
makes and breaks two
different circuits. Example,
(2) NO and (2) NC contacts.
Drip-Proof Enclosure—So
constructed or protected that
falling dirt or drops of liquid
will not interfere with the
successful operation of the
apparatus under specified
test conditions.
Dust-Tight Enclosure—So
constructed as to meet the
requirements of a specified
dust-tightness test.
Dwell Time—The time that
the target is present in the
sensing field and is detected
by the sensor.
Eddy Current—Current
induced into the body of a
metallic object by an
oscillating electromagnetic
field.
Effective Beam—The light
beam travelling directly
between a thru-beam source
and detector that must be
completely blocked for
detection to occur.