Precautions for prorer use - Photoelectric Sensors

The setting distance must be equal to or less than the specified sensing range.
The sensors may be operable at a setting distance longer than the rated sensing range, but reliable operation cannot be guaranteed. Further, in a dirty or dusty environment, the setting should provide margin for beam intensity reduction.

The sensing range given in the specifications is for the standard sensing object.
Since the actual sensing distance differs with the size, color, surface condition, etc., of the sensing object, set the sensor giving enough margin for these differences.

<Change of sensing range with sensing object size>

<Change of sensing range with sensing object> (Diffuse reflective type sensors)

The above mentioned relative sensing range for different sensing objects has been given taking the sensing range for white non-glossy paper as 100. The values are given for reference, and would vary slightly with the type of photoelectric sensor, sensing object size, etc.

If sensors are mounted adjacently, they may affect each other's operation (mutual interference). The following countermeasures are necessary to prevent it.

Countermeasure(1) : Use sensors having interference prevention function.

When sensors having the interference prevention function are used, sensors can be mounted close together.

Countermeasure(2) : Use interference prevention filters.

Countermeasure(3) : Increase the separation distance.

Find out the operating point ℓ1 on the parallel deviation diagram or the sensing field diagram for the setting distance L1. Separate sensors by 2 x ℓ1 or more.
(However, it is required that the emitter and receiver face each other and are installed in a direct line.)

Countermeasure(4) : Place the emitter and the receiver alternately. (Thru-beam type sensors only)

With this arrangement, if a sensing object comes near the sensors, the beam reflected from the sensing object may enter the receiver as shown below. In this case, countermeasures, such as placing a shield between the emitter and the receiver are necessary.

Placing a shield

Countermeasure(5) : Narrow the light beam with a hood or a slit mask. (Thru-beam type sensors only)

<Thru-beam type and retroreflective type sensors>

If a thru-beam type sensor, or a retroreflective type sensor is mounted on a flat shiny plane, the emitted beam may not be interrupted by a sensing object because some amount of the emitted beam passes through the gap between the sensing object and the plane, gets reflected from the plane, and enters the receiver.

Countermeasure(1) : Increase distance from the mounting plane.

Countermeasure(2) : Place light barriers on the mounting plane.

Place light barriers at (A), (B) and (C) to prevent reflection.

Countermeasure(3) : Paint the mounting plane in non-glossy black color.

<Reflective type sensors>

If a reflective type sensor is mounted on a rough plane, scatteredly reflected beam returns to the sensor.
This causes the hysteresis to increase or the sensor to always remain in the light received condition.

Countermeasure(1) : Increase distance from the mounting plane.

Countermeasure(2) : Paint the mounting plane in non-glossy black color.

If there is a wall, etc., behind the sensing object, the sensor operation may be affected.

Countermeasures

(However, the specular background should be a plane surface, directly facing the sensor. A spherical or curved background may be detected.)

Most of the sensors use modulated beam highly immune to sunlight or ordinary fluorescent light. However, intense light or light from inverter fluorescent lamps may affect the sensor operation.

Countermeasure(1) : Tilt the beam axis so that the receiver is not directly facing the extraneous light source.

The incident angle and wavelength of the sunlight vary depending on the seasons, time of day, or other reasons. Thus, the influence that the sunlight has on sensors changes. For this reason, make sure to confirm that a malfunction does not occur with actual sensors before use.

Countermeasure(2) : Attach a hood on the receiver.

Marks can be sensed with mark sensor LX-100 series or color fiber sensor FZ-10 series, mark sensor or fiber sensor.

LX-100 series

<When the mark mode is set>

The optimal light source is automatically selected from the 3 colors of the R, G, B LEDs so that the contrast between the mark and base becomes the largest. This makes detection more stable.

<When the color mode is set>

The color mode utilizes all the R, G, B LEDs and detects the reflected light by calculating the R, G, B ratio. Thus, high precision detection is possible by sensing only the mark color that teaching was performed on.

FZ-10 series

The FZ-10 series uses red, green and blue LEDs to identify a color by its three color components. Hence, it is able to discriminate even minute color differences.

Mark sensors, Fiber sensors

For mark sensors and fiber sensors, the color combinations of the mark and the background which can be discriminated, depending on the color of the light source, are as given in the table below.

(R)	:	Red LED type
(G)	:	Green LED type
(B)	:	Blue LED type