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Reliable Object Detection with the Through-Beam Mode

The through-beam principle is a functional principle in which a switching process is triggered as soon as the light beam is interrupted by an object. Sensors that work according to this principle are used in a wide range of applications.

Through-Beam Principle with wenglor Sensors

Design Variety

Use in various industries and harsh environments such as steam, mist, dust

High Flexibility

Precise object detection over long distances

High Reliability

Reliable detection of a wide range of objects, including deep black and glossy objects

Speed

High switching frequency and short response times

How the Through-Beam Principle Works

With the through-beam principle, the switching process is triggered when the light beam emitted by the emitter is interrupted by an object or a person so that no or less light hits the receiver optics. The light beam from the emitter to the receiver forms the “barrier”. There are also variants based on ultrasound. With this mode, an object can be detected reliably independent of color, shape and surface characteristics. Typical applications include production or packaging line monitoring, fill-level monitoring and object counting. In order to reliably secure systems and hazardous areas, there are special products with special requirements in the field of safety technology.

How Can a Through-Beam Solution Be Implemented?

Separate Emitter and Receiver

The emitter and receiver are located opposite each other in separate housings. This makes them ideal for longer distance applications. They also reliably detect opaque and reflective objects.

Sensor Solutions:

Emitter and Receiver in a Single Housing

Emitter and receiver can also be located opposite each other in an U-shaped housing. Typical for this is the small spatial distance between emitter and receiver. These sensors reliably detect the smallest parts and offer easy installation.

Sensor Solutions:

Retro-reflex sensor checks the presence of glass bottles

Emitter and Receiver in One Housing with a Reflector Opposite

The emitter and receiver are located in a housing, while a reflector is positioned on the opposite side. Reflex light barriers require only the use of a selectable background, thus eliminating the need for a reflector. This principle is particularly suitable for long-range applications and for detecting shiny, chrome-plated and transparent objects.

Sensor Solutions:

Retro-reflex sensors
Reflex light barriers
ToF laser distance sensors with reflector
Fiber-optic sensors with reflector

Comparison of Other Sensor Principles

Reflex Mode

The emitter and the receiver are integrated in a single housing. The transmission beam emitted by the emitter hits an object and is reflected to the receiver. The object is detected by the reflected light or by ultrasonic waves hitting the receiver.

Time-of-Flight Measurement Principle

The emitter emits light that is reflected back to the receiver by an object or reflector. The time interval from emission of the light pulse to the object and back is measured. The relevant distance to the object is determined by the time and the speed of the light.

Triangulation Principle

In this method, a light point is projected onto the object to be measured. The object reflects the light and hits a receiving element in the sensor at a certain angle. The distance is determined by the position of the light spot on the receiving element.

Energetic Principle

With the energetic principle, the intensity of the received signal is used for the evaluation.

Detection of Battery Cells with Retro-Reflex Sensors for Transparent Objects

During battery unit assembly, individual cells are grouped into modules. Previously tested cells that are unsuitable are separated and collected in so-called stations. The capacity of these collection points is monitored by retro-reflex sensors for transparent objects. If the number of available spaces exceeds a defined limit, the sensor triggers a signal.

Flap Query on Automotive Bodies via Light Curtains for Measuring Tasks

Light curtains for measuring tasks are used in several positions during car assembly to check the exact flap position of, for example, engine hoods or tailgate and to avoid possible collisions.

Safety Guard on High-Voltage Test Benches via Safety Light Curtains for Finger Protection

To prevent an operator from reaching into the test benches in the high-voltage and low-voltage area, the systems are protected with safety light curtains with finger protection. These are installed flush and in a space-saving way, so that no blind spots are created and the system is completely secured. The safety field is thus active over the entire housing length. If an intervention in the safety field is registered, the system stops immediately.

Zone Protection During Automated Handling of Plastic Parts Thanks to Safety Light Curtains with Hand Protection

Vertical and horizontal safety light curtains are installed at the removal points for zone protection of fully automatic robot cells in the production of trunk linings. These curtains react immediately to manual interventions or entry into the equipment and stop the machine.

Overhang Monitoring in Pallet Warehouses Using Through-Beam Sensors

In automated pallet warehouses, through-beam sensors are installed at the outer ends of the shelves on each level to immediately detect protruding pallets. The light barriers operate reliably over long distances and in the event of interference.

Presence Check of Pallets in the Deep-Freeze High-Bay Warehouse with Through-Beam Sensors

To ensure the presence of pallets before and after each transfer position, deep-freeze logistics centers use through-beam sensors. While solutions with reflectors do not offer process reliability due to contamination, the through-beam sensors switch reliably.

Ejection Control of Thin Shipping Bags on a Conveyor Belt Using Retro-Reflex Sensors with Light Band

In intralogistics, the sorting of thin shipping bags, so-called flats, must be monitored to ensure a smooth material flow. Retro-reflex sensors with light bands are installed on the sides of the ejection lanes, which accurately detect the flats from the front edge and over the entire width of the lane.

Height Control of Euro Pallets for Film Wrapping Units with Light Curtains for Measuring Tasks

Before wrapping goods on pallets, the exact height of the loaded pallet must be measured. For this purpose, a light curtain for measuring tasks is installed in front of the film wrapper, which determines the height of the goods and then wraps them sufficiently for shipping.

Zone Protection in Stretch Film Systems with Safety Light Arrays

In stretch film systems, the danger zone must be reliably secured. For this purpose, multi-beam safety light arrays are installed on the conveyor line so that the pallets can be safely fed in and out for the filming process.

Counting of Cannulae for Syringes with Through-Beam Sensors

Before packaging cannulae for syringes, it must be ensured that each packaging unit contains the correct number of objects. Through-beam sensors reliably detect and count the smallest parts, regardless of their shape, color or surface.

Position Control of Trays by Retro-Reflex Sensors

Before sealing trays with a film, it must be ensured that they are correctly positioned in the packaging lines. A retro-reflex sensor with laser light is mounted on the side of the conveyor belt and detects the top edge of the tray. The fine laser beam ensures that all trays to be sealed are correctly positioned and not higher than intended.

Position Control of Tools in Tray Sealing Machines with Fork Sensors

Shell sealing machines are used in the packaging industry to seal plastic trays with a foil cover under pressure and heat. In order to reliably detect the position of the tool, a miniature fork sensor is installed on the side, which reliably detects so-called switching flags on the tool despite the room for movement and regardless of their material and color.

Leading Edge Detection of Soft Cheese with Through-Beam Sensors

In soft cheese production, a through-beam sensor with an opposing receiver is installed on the side to detect the leading edges of the cheese pieces to trigger the packaging process of a special bagging machine, monitor the distance between the objects and prevent jams.

Detection of Red Plastic Boxes for Meat Products by Retro-Reflex Sensors

In meat production, meat and sausage products are transported in red plastic boxes on conveyor belts. After the packaging process, the empty boxes must be hygienically cleaned with high pressure and cleaning agents in special crate washing plants. A universal retro-reflex sensor with red light detects the incoming boxes and starts the washing process.

Position Monitoring of Crown Caps with Fork Sensors

In the beverage industry, forked sensors check the presence of caps on bottles. With their collimated light beam, they can also reliably detect transparent objects down to a size of just a few micrometers.

Discharge Control of Wooden Planks in Planing Machines via Through-Beam Sensors

A through-beam sensor is installed at the side of the outlet for safe entry and exit of wooden boards into wood planing machines. When the light beam is no longer interrupted by the wooden board and hits the receiver, the board has completely left the machine and a new object is drawn in.

Presence Check of Trunks on a Gang Saw with Through-Beam Sensors

In large sawmills, trunks are automatically transported away via a conveyor belt after sawing. A through-beam sensor is installed at the end of the machine. This reliably detects the presence of trunks even in harsh ambient conditions and with ambient light and activates the conveyor belt for removal.

Detection of Euro Pallets with Retro-Reflex Sensors

Smooth flow of goods on roller conveyors requires reliable detection of pallets. If the objects are conveyed in the same direction and position, a retro-reflex sensor installed on the side of the conveyor line is ideal for this detection. Precise point scanning via red light over the entire path width is possible thanks to the single-lens optics without blind spot.

Length Measurement of Trunks with Light Curtains for Measuring Tasks

To determine the length of tree trunks, light curtains for measuring tasks can be used. The light curtains cover the entire trunk cross-section and switch as soon as the leading edge interrupts the beams. The signal ends as soon as the trailing edge is reached. The length of the trunk in meters can be calculated from the duration of the switching signal in combination with the speed of the conveyor belt.

Hazard Area Protection in Window Profile Production with Safety Light Curtains for Hand Protection

Safety light curtains for hand protection are used in the production of window profiles for zone protection. When entering the safety zone, the machine stops immediately. The protective devices can monitor several areas over long distances and, depending on the structure of the areas, the system can continue to operate undisturbed in another zone despite the interruption.

Access Protection on a Stacking Device with Multi-Beam Safety Light Arrays

To ensure the safety of workers during automated loading and unloading of palletizing stations, safety light arrays are installed to protect the entire system. Entire surfaces can even be secured over corners using deflection mirrors.

PCB Detection on Transport Modules with Fiber-Optic Amplifier and Several Fiber-Optic Cables

To ensure safe transport of boards, fiber-optic cables with emitter and receiver are installed in the narrow side panels, which reliably detect the boards at each station.

Position and Presence Check of Connector Components via Fiber-Optic Sensors

When manufacturing plug connectors for high-voltage on-board electrical systems of electric and hybrid vehicles, fiber-optic cables are used to check for the presence and correct position of the plugs. Their compact format makes them ideal in areas where only very little space is available for querying.

Counting Small Electronic Components Using Fork Sensors

Miniature fork sensors are mounted on the conveyor belt to ensure that the correct number of parts always lands in the packaging of microelectronic components. The fork sensor counts and detects the objects regardless of their shape, color and position.

Tool Breakage Check on Drill and Milling Heads with Through-Beam Sensors

For automated turning, milling or drilling machines, the quality and condition of the drilling and milling heads must be checked every time the tool is changed. A through-beam sensor reliably detects the tool tip with a fine laser beam. If the light beam is not interrupted, the cutter head is shorter and therefore worn or broken.

Material Separation in Reverse Vending Machines Using Through-Beam Sensors

In reverse vending machines, the material of the inserted PET or glass bottles and cans is detected by a through-beam sensor, consisting of an emitter and receiver. In this way, the objects can be sorted and recycled.

Visitor Counting in Recycling Centers with Universal Retro-Reflex Sensors

At recycling centers, the daily number of visitors must be recorded in order to optimally plan the staff capacities at the centers. For this purpose, two universal retro-reflex sensors with laser light are installed at the entrance and exit gates. Depending on the signal sequence, both the number and the direction of travel can be detected.

Presence and Position Check of Labels for Hygiene Products with Ultrasonic Fork Sensor

Ultrasonic fork sensors are used in the production of care products to check the presence and position of labels on the carrier film. Different colored, dark, transparent, printed and very thin labels are reliably detected by the sensors at high speeds.

Overview of Solutions

Through-Beam Sensors

Through-beam sensors detect and count small parts, detect the edges of objects and monitor passages in systems. The emitter and receiver are housed in separate housings according to the through-beam mode. The sensor switches as soon as an object interrupts the laser light, red light or infrared light.

Fork Sensors

With fork sensors, the emitter and receiver are arranged opposite each other in a plastic or stainless steel housing. Fork sensors with collimated laser light beam are particularly effective for detecting the smallest objects or clear glass.

Retro-Reflex Sensors

Retro-reflex sensors work with different light sources, whereby the emitter and receiver are located in one housing. When the light beam between the emitter and the reflector is interrupted, a switching signal is output.

Fiber-Optic Sensors

Fiber-optic sensors in the through-beam model consist of an emitter and a receiver that are opposite each other and linked by a fiber-optic cable. As soon as the test object passes through the space between the emitter and receiver, the light of the fiber-optic cable is interrupted. Detection is performed by reducing the received light intensity.

Light Curtains for Measuring Tasks

Light curtains for measuring tasks detect and measure objects with infrared light according to the through-beam mode. The emitter and receiver are enclosed in separate housings and are available with different measuring field heights and beam distances. If the light beams are interrupted during a protrusion or height check, the sensor is switched.

Ultrasonic Fork Sensors

Ultrasonic fork sensors work according to the through-beam principle and detect labels on any label material regardless of color, transparency or surface finish. The label on the carrier material attenuates the ultrasound more strongly than the carrier material itself; a small gap is sufficient for differentiation.

Electro-Sensitive Protective Equipment

Electro-sensitive protective equipment for body, hand and finger protection detects the entry of a person or part of the body into a safety field by means of optical beams without direct mechanical contact. Electro-sensitive protective equipment is therefore used to protect hazardous areas on machines.

Sensors

Products	Benefits	Product links
Through-beam sensors	For long distance applications High functional reliability in the event of disturbing factors such as steam, mist or dust Variants available for PET selection	Go to products
Fork sensors	The emitter and receiver are in the same housing Reliable detection of even the smallest and transparent objects Ideally aligned transmitter-receiver axis at the factory	Go to products
Fiber-optic sensors	Ideal for detecting small parts Flexible adaptation through combination with different fiber-optic cables Reliable process thanks to dynamic readjustment of the switching threshold	Go to products
Light curtains for measuring tasks	Precise object detection and measurement Versatile due to different measuring field heights and beam distances	Go to products
Retro-reflex sensors	For detection of transparent and glossy objects Ideal for long-range applications	Go to products
Ultrasonic through-beam sensors	Reliable presence check of transparent, dark, glossy or complex objects Long-range applications possible	Go to products
Fork sensors for label detection	The emitter and receiver are in the same housing Material and color independent Resistant to contamination	Go to products
Safety light curtains for finger, hand and body protection	Effective safeguarding of hazardous areas on machines Reliable finger, hand and body protection Multiple sides can be secured via deflection mirrors	Go to products
Safety through-beam sensors	Reliable area and access protection for machines Can be used with the appropriate analysis module up to performance level c	Go to products


Products Through-beam sensors	Benefits For long distance applications High functional reliability in the event of disturbing factors such as steam, mist or dust Variants available for PET selection	Product links Go to products

Products Fork sensors	Benefits The emitter and receiver are in the same housing Reliable detection of even the smallest and transparent objects Ideally aligned transmitter-receiver axis at the factory	Product links Go to products

Products Fiber-optic sensors	Benefits Ideal for detecting small parts Flexible adaptation through combination with different fiber-optic cables Reliable process thanks to dynamic readjustment of the switching threshold	Product links Go to products

Products Light curtains for measuring tasks	Benefits Precise object detection and measurement Versatile due to different measuring field heights and beam distances	Product links Go to products

Products Retro-reflex sensors	Benefits For detection of transparent and glossy objects Ideal for long-range applications	Product links Go to products

Products Ultrasonic through-beam sensors	Benefits Reliable presence check of transparent, dark, glossy or complex objects Long-range applications possible	Product links Go to products

Products Fork sensors for label detection	Benefits The emitter and receiver are in the same housing Material and color independent Resistant to contamination	Product links Go to products

Products Safety light curtains for finger, hand and body protection	Benefits Effective safeguarding of hazardous areas on machines Reliable finger, hand and body protection Multiple sides can be secured via deflection mirrors	Product links Go to products

Products Safety through-beam sensors	Benefits Reliable area and access protection for machines Can be used with the appropriate analysis module up to performance level c	Product links Go to products

Product Flyer to Download

P1XD Product Flyer (902 KB)

This document provides an overview of the P1XD series fiber-optic amplifiers.

PNG//smart Product Flyer (961 KB)

This document contains the PNG//smart sensors product flyer. Photoelectronic Next Generation stands for a new age of smart photoelectronic sensors.

Ultrasonic Sensors Product Flyer (995 KB)

This document contains the product flyer for the ultrasonic sensors.

Safety Technology Product Flyer (1 MB)

This document provides an overview of wenglor’s safety technology products.

der wintec. Brochure (1 MB)

This document contains the brochure on long-range laser distance sensors with wintec (wenglor interference-free technology).

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