Cut Sheet

V8-A2-6 Volume 8—Sensing Solutions CA08100010E—November 2012 www.eaton.com
Appendix 2
Glossary of Terms
Normally Closed (NC)
Output—Solid-state output
configuration which emulates
a normally closed relay
contact condition.
Normally Open (NO)
Output—Solid-state output
configuration which emulates
a normally open relay contact
condition.
NPN (Current Sink)—The
sensor derives (“sinks”) its
current from the load.
Opaque—An opaque object
is impervious to the passage
of light through it. Opaque
objects offer high reliability in
sensing because they provide
the highest contrast between
light beam blocked and
unblocked conditions. See
also Contrast and
Translucent.
Operate Point—The point, at
a distance from the sensor
face, at which a target is
detected.
Operating Force—That
straight line force in the
designated direction applied
to the actuator to cause the
switch contacts to snap to
the operated contact position.
Operating Mode—See Light
Operate and Dark Operate.
Operating Position (O.P.)—
The position of the actuator at
which the contacts snap to
the operated contact position.
Outdoor Enclosure—
Suitable for installation where
exposed to the weather.
Over-Travel (O.T.)—The
movement of the actuator
beyond the contact trip
position without damage
occurring to the switch.
Perfect Prox
®
—A sensor
used to detect an object at or
inside a given range while
ignoring a nearby
background.
Photoelectric Sensor—An
electronic device capable of
recognizing changes in light
intensity and converting
these changes into a change
in output state. It is also
referred to as a “Photoeye.”
PNP (Current Source)—The
sensor provides (“sources”)
the current to the load.
Polarized Reflex Sensor—A
reflex photoelectric sensor
that uses a visible light
source, polarizing filters and a
prismatic retroreflector to
help the sensor distinguish
light returning from the
retroreflector from that
returning from a shiny target
surface, thus increasing the
reliability of the sensing
application.
Positive Opening Operation
(on NC contacts)—The
achievement of contact
separation as the direct result
of a specified movement of
the switch actuator through
non-resilient members (for
example not dependent upon
strings). Also called Direct
Opening and Positive Break.
Precision Snap-Action
Switch—A mechanically
operated electric switch
having predetermined and
accurately controlled
characteristics.
Pre-Travel (P.T.)—The
distance or angle through
which the actuator moves
before reaching the point at
which the contacts are
tripped.
Programmable Output—
Sensor output functions that
can be wired to output
normally open or normally
closed, but not
simultaneously.
Proximity Sensor—See
Inductive Proximity Sensor.
Radio Frequency
Interference (RFI)—
Interference caused by radio
transceiver signals (for
example, walkie talkie
devices).
Rainproof Enclosure—So
constructed, protected or
treated as to prevent rain
under specified conditions
from interfering with
successful operation of the
apparatus.
Receiver—See Thru-Beam
Detector.
Reference Axis—The axis
that is perpendicular to and
passes through the center of
the sensor face.
Reflex Sensing—A sensing
mode where source light
emitted from the sensor is
reflected directly back to the
detector by a prismatic
retroreflector. When this light
beam is blocked by a target,
the sensor changes output
state.
Release Force (R.F.)—
Amount of force still applied
to switch plunger or actuator
at the moment contacts snap
from the operated position to
the uno
perated po
sition.
Release Poi
nt—The point, at
a distance from the sensor
face, at which the target is no
longer detected by the
sensor.
Release Time—The time
delay from when a target
reaches the release point to
when the output restores to
the not operated state.
Repeat Accuracy—
Variations in sensing distance
between successive sensor
operations due to component
tolerances when all operating
conditions are kept constant.
Resistance—The opposition
to the flow of electricity in an
electric circuit measured in
ohms.
Response Time—Time
interval from when the target
reaches the operate point to
when the output goes into
the operated state.
Retroflective Sensing—See
Reflex Sensing.
Retroreflector—A highly
reflective material that
returns light that strikes it
back in a direction parallel to
its original course.
Return Force—Amount of
force still applied to a switch
plunger or actuator at the
moment the contacts snap
from the operated position to
the unoperated position.
Reverse Polarity
Protection—Internal circuitry
that prevents damage to the
sensor in case of accidental
reverse polarity connection
(plus-to-minus, minus-to-
plus).
Rust-Resistant Enclosure—
So constructed, protected or
treated that rust will not
exceed a specified limit when
subjected to a specified rust-
resistance test.
Semi-Shielded—An
inductive style that still
requires a metal-free zone
around the sensor face, but
the required area is greatly
reduced. Range for this type
is typically two to three times
the range of a similar shielded
sensor.
Sensing Face—The surface
from which the sensing field
is projected from a sensor.
Normally closed
Normally open
Symbol representing
positive opening
NC contacts