Photoelectric sensors

Photoelectric sensors for industrial applications

Photoelectric sensors are devices that use light—typically infrared or visible red—to detect the presence, shape, colour, distance or thickness of an object. Their non-contact operation, accuracy, and fast response make them essential in industrial automation, offering a modern and durable solution for reliable object detection across various applications.

Photoelectric sensors - structure and function

Photoelectric sensors operate based on how light interacts with various surfaces—through absorption, reflection, refraction or scattering. These interactions can occur with materials such as metal, glass or plastic.

Each sensor comprises three main components:

• Emitter – produces the light beam

• Receiver – detects the light

• Signal processor – converts light changes into an electrical signal

When an object interrupts or reflects the light beam, the sensor registers this change and sends an output signal, allowing precise object detection without physical contact.

How photoelectric sensor works​

Main operating principles

There are three common operating modes:

• Through-beam (transmissive)
  The emitter and receiver are positioned opposite each other. The object is detected when it blocks the beam. This mode offers the longest sensing range and highest accuracy.

• Retro-reflective
  The emitter and receiver are housed together, facing a reflector. Detection occurs when an object interrupts the reflected beam. Suitable for detecting opaque objects over moderate distances.

• Diffuse (reflective)
  The emitter and receiver share the same housing, with detection based on light reflected directly from the object. Best for short-range detection of reflective or light-coloured surfaces.

How to test photoelectric sensor

o ensure reliable operation, follow these steps:

1. Supply power
   Connect the sensor to the rated voltage (typically 10–30 V DC) and ensure wiring is correct.

2. Observe the LED indicator
   The built-in LED provides visual feedback. Check the datasheet to interpret the indicator’s signals for your model.

3. Test detection
   Simulate object detection:

   • Through-beam: Block the beam between emitter and receiver.

   • Retro-reflective: Insert an object between the sensor and reflector.

   • Diffuse: Place an object within sensing range.

4. Move object in and out of range
   Check that the LED and output respond consistently to object movement.

5. Confirm output signal
   If connected to a controller or PLC, verify signal changes using a multimeter or monitoring system.

6. Inspect and clean the optics
   Remove any dust, oil or debris from the lens to maintain accuracy.

7. Check alignment and range
   Ensure proper alignment and verify the object is within range. Adjust sensitivity settings if needed.

How to adjust photoelectric sensor​

Proper adjustment ensures consistent and accurate detection. Follow these steps:

1. Mount the sensor securely
   Fix the sensor on a stable surface and align it correctly. Movement during use can affect accuracy.

2. Power the sensor
   Connect to a suitable power supply and confirm the LED is active.

3. Align the sensor

   • Through-beam: Align emitter and receiver directly.

   • Retro-reflective: Align the sensor with the reflector.

   • Diffuse: Aim the sensor at the target object.

4. Adjust sensitivity
   Use the potentiometer or adjustment button:

   • Diffuse: Set to detect the target while ignoring background surfaces.

   • Retro-reflective: Adjust to detect the reflector and avoid false triggers from shiny or transparent items.

   • Through-beam: Usually minimal adjustment is needed if alignment is correct.

   Tip: Start with high sensitivity, then reduce gradually until the sensor detects only the intended object.

5. Test for background rejection
   Ensure the sensor only responds to the target object and not to nearby surfaces.

6. Lock settings
   If your sensor supports it, enable the lock feature to prevent accidental adjustments.

7. Monitor performance
   Observe the sensor in regular operation and re-adjust if environmental conditions change (e.g. dust, lighting, temperature).

In which industries is an optoelectronic sensor used?

Our range of brands is rich in a variety of photoelectric sensors that are used in many industries. Customers can opt for M18 type optical sensors, which are used in the food and beverage industry, among others. These sensors are characterized by exceptional resistance to harsh industrial conditions - the high degree of protection IP 69K qualifies our sensors for use in digital food production halls in wet areas where aggressive cleaning agents are used. The robust sensor housing made of high-quality stainless steel also enables precise monitoring of objects, e.g. in breweries, the meat processing industry or cheese production.

The product range of ifm electronic also includes the photoelectric distance sensors OMH, which are used e.g. on high-speed conveyor belts, where they enable frequency measurement of up to 1200 Hz in speed mode and detection of small objects with a resolution of up to 0.01 millimeters. OMH optical sensors are characterized by exceptional functional accuracy, so they also enable the precise positioning and stacking required, for example, in the manufacture of battery cells.

Optical sensors for special applications

Ifm electronic customers can also opt for photoelectric distance sensors that have been developed for somewhat more demanding industrial processes with a high degree of automation. High-resolution color sensors are particularly suitable for the packaging industry - these devices recognize, among other things, the color of products and packaging as well as labels and prints.

An optical sensor for non-contact level measurement of bulk solids and opaque liquids can also prove useful. These sensors use the pmd time-of-flight technology for a distance measurement: light waves emitted by the laser light source propagate, when they are reflected by the target object, the phase pattern shifts and this shift is directly proportional to the distance.

Pharmaceutical and food companies also like to use sensors to detect transparent objects. The sensors for detecting transparent objects consist of a reflex light barrier with a polarizing filter and a very fine triple mirror. Their main function is to efficiently count bottles and jars and check the condition of the film for possible damage.

Do you want to increase the efficiency of your company? Rely on the innovative products from ifm electronic.

Modern optical sensors are an extremely useful solution that more and more companies in the industrial sector are opting for every year. They enable accurate and reliable detection of objects without affecting their parameters. Are you interested in our offer? Find out about the entire product range from ifm electronic and find out more about the additional functionalities of the innovative optoelectronic sensors.