Photoelectric sensors

Photoelectric sensors for industrial applications

Photoelectric sensors use light to detect the presence, absence, position or distance of an object without physical contact. Across Australian manufacturing, food and beverage processing, logistics, water treatment and OEM machinery, they are commonly used to monitor products, packages, pallets, containers and machine movements where reliable object detection is critical to production performance. 

The correct sensor is not selected by shape alone. It depends on the sensing principle, target material, sensing distance, available mounting space, required switching output, washdown exposure and whether distance data or diagnostics are needed through IO-Link. 

How do they work?

A photoelectric sensor contains an emitter, receiver and signal processor. The emitter produces light, typically visible red or infrared, and the receiver monitors the returned or interrupted light signal. When the target interrupts, reflects or changes the received light, the sensor converts that change into an electrical output for a PLC, controller or machine input.

Main photoelectric sensing principles

• Through beam sensors: uses a seperate emitter and receiver installed opposite each other. The sensor changes output state when the object interrupts the beam between two devices.
• Retro-reflective sensors: places the emitter and receiver in one housing and uses a reflector opposite the sensor. Detection occurs when the target interrupts the light returning from the reflector.
• Diffuse reflection sensors: has the emitter and receiver in one housing and detects the light directly from the reflector.
• Background supression sensors: designed to detect the target while reducing unwanted switching from the objects or surfaces behind it. ifm supplies multiple background supression families.
• Laser distance sensors: measure distance rather than only switching on object presence. ifm O1D laser sensors provide long-range optical distance measurement with IO-Link, while O5D sensors use PMD time-of-flight technology for compact distance detection up to 2m depending on the model.

Common Applications

Photoelectric sensors are used across a wide range of Australian industries to detect, count, position and verify products, packages, pallets, components and machine movements throughout automated processes.

Food and Beverage Processing

Photoelectric sensors are commonly used for bottle detection, carton counting, packaging verification, conveyor monitoring and product flow throughout food, beverage, and dairy facilities. In washdown areas, sensor housings and ingress protection ratings are often as important as sensing performance.

Typical sensor types:

• Retro-reflective sensors for bottle, carton and package detection on conveyors
• Through-beam sensors for high-speed counting and reliable object detection
• Background suppression sensors for detecting products in confined equipment with nearby machine surfaces

Packaging and Conveying Systems

Packaging machinery relies on accurate object detection to prevent jams, miscounts, and production interruptions. Sensors are often used to detect cartons, trays, shrink-wrapped products, and product accumulation points.

Typical sensor types:

• Through-beam sensors for carton counting and high-reliability detection
• Retro-reflective sensors where only one side of the conveyor is accessible
• Diffuse sensors with background supression for package presence verification
• Colour and contrast sensors for label and packaging-mark detection

Warehousing and Intralogistics

Distribution centres, warehouses and automated material handling systems use photoelectric sensors to detect pallets, cartons, totes and moving assets within conveyor and sortation systems.

Typical sensor types:

• Through-beam sensors for longer conveyor sections
• Retro-reflective sensors for pallet and carton detection
• Laser distance sensors (O1D, O5D, O6D, OGD) for position verification and accumulation monitoring
• Fork sensors for object counting and detection in automated systems

Water and Wastewater Facilities

Photoelectric sensors are used throughout water and wastewater treatment plants for detection and monitoring tasks on screening equipment, conveyors, chemical dosing systems, sluice gates, tank access points and other automated process equipment. Their non-contact operation can help reduce wear and maintenance compared to mechanical switching devices in wet or contaminated environments.

Typical sensor types:

• Through-beam sensors for reliable detection over long distances
• Photoelectric distance sensors for gate position, equipment movement and process monitoring
• IP67 and IP69K sensors for areas exposed to moisture, spray, washdown or condensation