Photoelectric Sensors

Photoelectric technology

A photoelectric sensor basically comprises a light beam transmitter (light-emitting diode) and a light-sensitive receiver (photo-transistor). A light-emitting diode is an electronic semi-conductor component that emits light when an electric current flows through it. This light can be visible or invisible, depending on the transmission wavelength.

Detection occurs when an object enters the transmitted light beam and, in so doing, affects the intensity of the light at the receiver. As the light intensity at the receiver decreases, a point is reached whereby the output of the sensor changes state.

Depending on the model and application requirements, the transmission beam is either non-visible infrared (which is most common) or ultraviolet (for detection of luminescent materials). It may also be a visible red or green (for color mark reading etc.) and laser red (for long sensing distance and short focal length).

The advantage of LEDs is their very fast response. To render the system insensitive to ambient light, the current flowing through the LED is modulated to produce a pulsed light transmission. Only the pulsed signal will be used by the photo-transistor and processed to control the load.

Listed below are different variations of the XU range, each accompanied by a description to help you choose the perfect photoelectric solution.

Through-beam system or multimode set in through-beam mode

Advantages

• Long sensing distance (up to 100m (XUBL line))
• Very precise detection, high repeat accuracy.
• Detection not affected by colour of object or by position angle.
• Good resistance to difficult environments (dust, grime, etc.).

Drawbacks

• 2 units to be wired.
• The object to be detected must be opaque & solid
• Precise alignment required, which can be difficult since the sensor transmits in the infrared range (invisible).

Operating precautions

• When several sensors are used, care must be taken to ensure that no sensor is disrupted by another sensor (solutions include alternate mounting of the transmitter and receiver, etc.).

Polarised reflex system or multimode with reflector accessory

Advantages

• Medium sensing distance (up to 15 m).
• Precise detection.
• Only one unit to be wired.
• Detection not affected by colour of object or by position angle
• Visible red beam transmission

Drawbacks

• Precise alignment required.
• The object to be detected must be opaque and larger than the spot light.

Operating precautions

• When several sensors are used, they must be aligned in such a manner that no sensor is disrupted by another sensor.
• For short distance detection use a reflector with large trihedrons, type XUZC24.
• For long distance detection use a reflector XUZC50 or XUZC80.
• To increase the sensing distance use reflector XUZC100.
• If reflective tape is used, use rolls of tape XUZB1 or XUZB15 which are specially adapted for polarised reflex systems.

Advantages of multimode sensor with reflector accessory

Easy alignment

• 3 LEDs providing setting-up assistance.
• The anti-interference function enables 2 sensors to be used without specific alignment precautions.

Semi-transparent objects can be detected by using the teach mode function.

Diffuse system or multimode

Advantages

• Only one unit to be wired.
• Easy to use
• Fast response.
• Low cost.

Drawbacks

• Short sensing distance.
• Sensitivity to object or background colour differences. Sensitive to the environment (dust or dirty)
• Object sighting line difficult since the sensor transmits in the infrared range (invisible).

Operating precautions

• When several sensors are used, they must be aligned in such a manner that no sensor is disrupted by another sensor.

Advantages of a multimode sensor

• Easy alignment:
  • the sensor transmits in the visible red range during the alignment phase,
  • 3 LEDs providing setting-up assistance,
  • the anti-interference function enables 2 sensors to be used without specific alignment precautions.
• Refined detection: the position of the object can be detected using the teach mode

Diffuse, with or without background suppression, system or multimode

Advantages

• Only one unit to be wired.

Drawbacks

• Sensing distance affected by colour.
• Short sensing distance.
• Object sighting line difficult since the sensor transmits in the infrared range (invisible).

Operating precautions

• Detection can be affected by the object's direction of movement. To overcome this phenomenon (the hat effect), it is recommended that the sensor is mounted so that the object simultaneously breaks the beam of both lenses.
• When several sensors are used, they must be aligned in such a manner that no sensor is disrupted by another sensor.

Advantages of a multimode sensor

• Easy alignment:
  • the sensor transmits in the visible red range during the alignment phase,
  • 3 LEDs providing setting-up assistance,
  • the anti-interference function enables 2 sensors to be used without specific alignment precautions,
  • the hat effect is minimized using the background teach mode.
• Refined detection: the position of the object can be detected using the teach mode.

Optical forks

Constructed from metal, the optical fork is a robust sensor that is particularly suited to

conveying and packaging applications and detection of labels.

• Rugged optical detection device not requiring alignment in through-beam mode.
• The beam from the transmitter limb is transmitted to the receiver limb. Due to its construction, only one connection is required as opposed to two for a traditional through-beam function.
• The transmission sources are LEDs of various technologies:
  • Red for much improved efficiency during adjustment and maintenance
  • Red laser for detection of transparent materials or very small parts
  • Infrared, particularly for optical frames
  • Ultrasonic for detection of transparent labels (clear on clear)
• The beam is adjustable or fixed depending on the version. Adjustment enables the sensitivity to be altered and, therefore, detection of small parts down to dimensions of less than tenths of millimeters (minimum size of detectable object: 0.05 mm).
• The high switching frequency (from 4 kHz up to 25 kHz) is very useful in industrial applications involving high operating rates.

Fiber optics

The fiber acts as a light conductor. Light rays entering the fiber at a certain angle are conveyed to the required location, with minimum loss.

• Separate amplifier.
  • Size kept to minimum.
  • This system enables detection of very small objects (approximately 1 mm).
  • And, detection is very precise.

All our sensors are available either in pre-cabled version (except XUX; screw terminal with cable gland version) or connector version.

The connectors used are M12 (4-pin), M8 (4-pin) or 1/2" 20UNF (3-pin).

Through-beam systems. Polarized reflex systems. Diffuse systems. With background suppression. Without background suppression. Optical forks. Fiber optics.

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