To maximize contrast, position the lightest possible background to be used, at the closest position it will come to the sensor during use.

Using a small screwdriver in the adjustment screw, adjust the cutoff distance until the threshold is reached and the green Light Sensed

indicator changes state. If the indicator never turns ON, the background is beyond the maximum sensing cutoff and will be ignored.

Note the position of the rotating cutoff position indicator at this position. Then repeat the procedure, using the darkest target, placed in

its most distant position for sensing. Adjust the cutoff so that the indicator is midway between the two positions.

Target

Background

Cutoff

Distance

E

R2

R1

Figure 3. Set the cutoff distance approximately midway between the

farthest target and the closest background

ON

OFF

DELAY

DELAY

DO

SIG

LO

RANGE

tan

ce

Set Cutoff Midway

Between

Farthest Target Object

Closest Background

Figure 4. Setting the cutoff distance

Note: Setting the cutoff distance adjustment screw to its maximum clockwise position places the receiver lens

directly in front of the receiver elements and results in the Q60 performing as a long-range diffuse sensor.

Sensing Reliability

For highest sensitivity, the sensor-to-object distance should be such that the object will be sensed at or near the point of maximum

excess gain. The excess gain curves show excess gain versus sensing distance for 200 mm, 1200 mm, and 2 m cutoffs. Maximum excess

gain for a 200 mm cutoff occurs at a lens-to-object distance of about 150 mm, and for a 2 m cutoff, at about 500 mm. The background

must be placed beyond the cutoff distance. Following these two guidelines makes it possible to detect objects of low reflectivity, even

against close-in reflective backgrounds.

Background Reflectivity and Placement

Avoid mirror-like backgrounds that produce specular reflections. A false sensor response occurs if a background surface reflects the

sensor's light more to the near detector (R1) than to the far detector (R2). The result is a false ON condition (Figure 5 on page 4).

Correct this problem by using a diffusely reflective (matte) background, or angling either the sensor or the background (in any plane) so

the background does not reflect light back to the sensor (Figure 6 on page 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 7 on page 5), or moving past the

face of the sensor in a direction perpendicular to the sensing axis, may cause unwanted triggering of the sensor if more light is reflected

to the near detector than to the far detector. Correct the problem by rotating the sensor 90° (Figure 8 on page 5). 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.

Cutoff

Distance

Reflective

Background

Sensing

Field

E

R2

R1

E

= Emitter

R1 = Near Detector

R2 = Far Detector

Core of

Emitted

Beam

Strong

Direct

Reflection

to R1

Figure 5. Reflective Background - Problem

E

R2

R1

E

= Emitter

R1 = Near Detector

R2 = Far Detector

Cutoff

Distance

Reflective

Background

Strong

Direct

Reflection

Away From

Sensor

Sensing

Field

Core of

Emitted

Beam

Figure 6. Reflective Background - Solution

Q60LAF Series Laser Adjustable-Field Sensors

4

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