Through beam sensor

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An emitter in a separate housing transmits the light to a separate receiver. The object is detected when it breaks the emitted beam.

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The active area (A) of a through beam sensor is equal to the diameter of the lens of  the receiver or emitter. The acceptance zone (B) of the emitter and receiver is larger. However, this is only important for adjustment and for operation close to glossy surfaces. With focused through beam laser sensors, the active area is the diameter of the laser beam if this is smaller than the receiver lens or the front opening at the receiver end.

Characteristics and advantages

Due to the separated configuration, long ranges with large signal excess gain can be achieved in comparison with equivalent retro-reflective systems. Through beam-sensors are therefore most suitable for operation in unfavorable ambient conditions such as dirt, dust and moisture.

Mounting and adjustment

The emitter and receiver must be aimed at each other. The narrower the angle of radiation and reception, the more accurately this must be conducted.


Retro-reflective sensors

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The emitter and receiver are installed in the same housing. The emitted infrared, red or laser light is returned by a triple reflector or a reflective film to the receiver. The output changes its state when the object breaks the light beam (sensor receives no light).

Characteristics and advantages
Mounting and adjustment

Each sensor has a separate excess gain curve. As the operating reliability depends heavily on the ambient conditions, it must be ensured that the sensor operates with the highest possible excess signal gain.


Light barrier without reflector

SmartReflect

Contrary to diffuse or through beam sensors, SmartReflect light barriers feature a closed light beam which is set up between the sensor and machine. The sensor switches when an object interrupts the light beam. The only requirement is the presence of a defined background, e.g. a machine part, within the sensing range of the sensor, which closes the light beam.

Characteristics and advantages

Maximum security

Reduced operating costs

 

Mounting and adjustment

The SmartReflect light barrier has to be aligned with a machine part within its sensing range. This machine part is then set using the teach-in.


Diffuse sensor with background suppression

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By using the triangulation principle, diffuse sensors with background suppression not only measure the light intensity reflected by the target, but also determine the distance of the object from the sensor. In this way, objects with the minimum size of the light beam located within the adjustable sensing distance can be detected regardless of their color and surface.

The diffuse sensors with background suppression and laser light source were developed specifically for applications in which exact positioning is important. With the precisely focused beam, even very small objects such as the wires of a resistor or threads can be clearly detected or counted.

Characteristics and advantages
Mounting and adjustment

The diffuse sensor must be aimed at the object. The sensing distance must be set to a distance between the target and the background. The background must be located behind the adjusted sensing distance by at least the distance of the sensing distance reduction of the sensor to black.


Diffuse sensors with intensity difference

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The emitter and receiver are in the same housing. The emitted infrared, red or laser light is reflected directly by the target back to the sensor. If the target reflects sufficiently well, the received light causes the sensor to switch.

The light shining on the target is largely diffused and reflected back in all directions. A very small part of this remitted light is observed by the receiver. If the target reflects sufficiently well, the received light causes the sensor to switch. As the sensor operates with the reflection from the materials, the surface properties, color and gloss have a great influence on the switching distance.

Characteristics and advantages
Mounting and adjustment

With diffuse sensors operating by the intensity difference principle, the relative receiving signal is specified. This represents the signal level received from a white object as a function of the distance.


Retro-reflective sensors for transparent objects

The emitter and receiver are installed in the same housing. The emitted infrared, red or laser light is returned by a triple reflector or a reflective film to the receiver. The output changes its state when the object breaks the light beam (sensor receives no light). 

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A polarizing filter permits the emitted light to pass in only one polarization plane. The triple reflector depolarizes the light on reflection. A part of the light reflected back to the receiver passes the second polarization filter, offset by 90°, and is detected by the receiver.

Characteristics and advantages
Mounting and adjustment

Each sensor has a separate excess gain curve. As the operating reliability depends heavily on the ambient conditions, it must be ensured that the sensor operates with the highest possible excess signal gain.


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Mounting and adjustment

The emitter and receiver must be aimed at each other. The narrower the angle of radiation and reception, the more accurately this must be conducted.

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