T18 Sensors – ac-Voltage Series
P
Self-contained ac-operated sensors
Features
• Featuring EZ-BEAM® technology, the specially-designed optics and electronics
provide reliable sensing without the need for adjustments (most models)
• “T” style plastic housing with 18 mm threaded lens mount
• Models available in opposed, retroreflective, diffuse and fixed-field modes
• Completely epoxy-encapsulated to provide superior durability, even in harsh
sensing environments to IP69K
• Innovative dual-indicator system takes the guesswork out of sensor performance
monitoring
• 20 to 250V ac (3-wire hookup); SPST solid-state switch output, maximum
load 300 mA
Models
Sensing Mode Range LED Output Model*
Opposed
Retroreflective
with Gain Control
Polarized
Retroreflective
–
20 m (66')
Infrared
950 nm
†
2 m (79")
†
Visible Red
680 nm
LO
DO
LO
DO
LO
DO
T183E
T18AW3R
T18RW3R
T18AW3L
T18RW3L
T18AW3LP
T18RW3LP
Diffuse
with Gain Control
Fixed-Field
* Standard 2 m (6.5') cable models are listed.
• 9 m (30') cable: add suffix “W/30” (e.g., T183E W/30).
4-pin Micro-style QD models: add suffix “Q1” (e.g., T183EQ1). A model with a QD connector requires a mating cable. (See page 7.)
•
†
Use polarized models when shiny objects will be sensed.
300 mm (12")
25 mm (1") cutoff
Infrared
880 nm
50 mm (2") cutoff
100 mm (4") cutoff
LO
DO
LO
DO
LO
DO
LO
DO
T18AW3D
T18RW3D
T18AW3FF25
T18RW3FF25
T18AW3FF50
T18RW3FF50
T18AW3FF100
T18RW3FF100
WARNING . . . Not To Be Used for Personnel Protection
Never use these products as sensing devices for personnel protection. Doing so could lead to serious injury or death.
These sensors do NOT include the self-checking redundant circuitry necessary to allow their use in personnel safety
applications. A sensor failure or malfunction can cause either an energized or de-energized sensor output condition.
Consult your current Banner Safety Products catalog for safety products which meet OSHA, ANSI and IEC standards for
personnel protection.
Printed in USA 01/05 P/N 121525
Sensing
Axis
R1
R2
E
R1
R2
Lenses
Object
A
Object B
or
Background
Sensing
Range
Cutoff
Distance
E
Receiver
Elements
Near
Detector
Far
Detector
Emitter
Object is sensed if amount of light at R1
is greater than the amount of light at R2
T18 Sensors – ac-Voltage Series
Fixed-Field Mode Overview
T18 Series self-contained fixed-field sensors are small, powerful, infrared diffuse mode
sensors with far-limit cutoff (a type of background suppression). Their high excess gain
and fixed-field technology allow them to detect objects of low reflectivity, while ignoring
background surfaces.
The cutoff distance is fixed. Backgrounds and background objects must always be placed
beyond the cutoff distance.
Fixed-Field Sensing – Theory of Operation
The T18FF compares the reflections of its emitted light beam (E) from an object back to the
sensor’s two differently aimed detectors, R1 and R2 (see Figure 1). If the near detector (R1)
light signal is stronger than the far detector (R2) light signal (see object A, closer than the
cutoff distance), the sensor responds to the object. If the far detector (R2) light signal is
stronger than the near detector (R1) light signal (see object B, beyond the cutoff distance),
the sensor ignores the object.
The cutoff distance for model T18FF sensors is fixed at 25, 50 or 100 millimeters (1", 2",
or 4"). Objects lying beyond the cutoff distance usually are ignored, even if they are highly
reflective. However, it is possible to falsely detect a background object, under certain
conditions (see Background Reflectivity and Placement).
In the drawings and discussion on these pages, the letters E, R1, and R2 identify how the
sensor’s three optical elements (Emitter “E”, Near Detector “R1”, and Far Detector “R2”)
line up across the face of the sensor. The location of these elements defines the sensing
axis (see Figure 2). The sensing axis becomes important in certain situations, such as those
illustrated in Figures 5 and 6.
Figure 1. Fixed-field concept
Sensor Setup
Sensing Reliability
For highest sensitivity, position the target object for sensing at or near the point of
maximum excess gain. The excess gain curves for these products are shown on page 5.
They show excess gain vs. sensing distance for sensors with 25 mm, 50 mm, and 100 mm
(1", 2", and 4") cutoffs. Maximum excess gain for the 25 mm models occurs at a lens-toobject distance of about 7 mm; for 50 mm models, at about 10 mm; and for the 100 mm
models, at about 20 mm. Sensing at or near this distance will make maximum use of
each sensor’s available sensing power. The background must be placed beyond the cutoff
distance. (Note that the reflectivity of the background surface also may affect the cutoff
distance.) Following these two guidelines will improve sensing reliability.
Background Reflectivity and Placement
Avoid mirror-like backgrounds that produce specular reflections. False sensor response will
occur if a background surface reflects the sensor’s light more strongly to the near detector,
or “sensing” detector (R1), than to the far detector, or “cutoff” detector (R2). The result
is a false ON condition (Figure 3). To cure this problem, use a diffusely reflective (matte)
background, or angle either the sensor or the background (in any plane) so the background
does not reflect light back to the sensor (see Figure 4). Position the background as far
beyond the cutoff distance as possible.
An object beyond the cutoff distance, either stationary (and when positioned as shown in
Figure 5), or moving past the face of the sensor in a direction perpendicular to the sensing
axis, can cause unwanted triggering of the sensor if more light is reflected to the near
detector than to the far detector. The problem is easily remedied by rotating the sensor
90° (Figure 6). The object then reflects the R1 and R2 fields equally, resulting in no false
triggering. A better solution, if possible, may be to reposition the object or the sensor.
2 P/N 121525
As a general rule, the most reliable
sensing of an object approaching from the
side occurs when the line of approach is
parallel to the sensing axis.
Figure 2. Fixed-field sensing axis
Banner Engineering Corp. • Minneapolis, MN U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
Fixed
Sensing
Field
Reflective
Surface
or
Moving Object
Cutoff
Distance
R1 = Near Detector
R2 = Far Detector
E = Emitter
T18FF
R1
E
R2
Fixed
Sensing
Field
Reflective
Surface
or
Moving Object
Cutoff
Distance
R1 = Near Detector
R2 = Far Detector
E = Emitter
T18FF
R1
E
R2
Fixed
Sensing
Field
R1 = Near Detector
R2 = Far Detector
E = Emitter
T18FF
Cutoff
Distance
Reflective
Surface
or
Moving Object
R1, R2, E
E
R2
R1
T18FF Sensor
R1 = Near Detector
R2 = Far Detector
E = Emitter
Core of
Emitted
Beam
Cutoff
Distance
Reflective
Background
Fixed Sensing
Field
Strong
Direct
Reflection
Away
From Sensor
T18 Sensors – ac-Voltage Series
Color Sensitivity
The effects of object reflectivity on cutoff distance, though small, may be important for
some applications. It is expected that at any given cutoff setting, the actual cutoff distance
for lower reflectance targets will be slightly shorter than for higher reflectance targets (see
Figure-of-Merit information on page 5). This behavior is known as color sensitivity.
For example, an excess gain of 1 (see page 5) for an object that reflects 1/10 as much light
as the 90% white card is represented by the horizontal graph line at excess gain = 10. An
object of this reflectivity results in a far limit cutoff of approximately 20 mm (0.8"), for the
25 mm (1") cutoff models for example; thus 20 mm represents the cutoff for this sensor
and target.
These excess gain curves were generated using a white test card of 90% reflectance.
Objects with reflectivity of less than 90% reflect less light back to the sensor, and thus
require proportionately more excess gain in order to be sensed with the same reliability as
more reflective objects. When sensing an object of very low reflectivity, it may be especially
important to sense it at or near the distance of maximum excess gain.
Figure 3. Reflective background – problem Figure 4. Reflective background – solution
A reflective background object in this position or
moving across the sensor face in this axis and
direction may cause false sensor response.
A reflective background object in this position or
moving across the sensor face in this axis will be
ignored.
Figure 5. Object beyond cutoff – problem Figure 6. Object beyond cutoff – solution
Banner Engineering Corp. • Minneapolis, MN U.S.A.
P/N 121525 3
www.bannerengineering.com • Tel: 763.544.3164
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