Selection Criteria
Operating environment compatibility: Resistance to environmental conditions such as temperature range, humidity, dust, and vibration.
Output signal type: Analog (4–20 mA, 0–10 V) or digital (PNP, NPN, IO-Link) outputs must be compatible with the controller infrastructure.
Sensing distance and resolution: The application's accuracy requirements determine the sensor's nominal sensing range.
IP protection rating: Industrial environments generally require at least IP67.
Response time: High-speed production lines may require sensors with sub-millisecond response times.
Quick Comparison Table
Sensor Type | Key Capability | Best Applications |
|---|---|---|
Inductive proximity | Metal object detection | Metal processing lines |
Capacitive proximity | Metal and non-metal detection | Food processing, packaging |
Photoelectric | Long-range, high-speed detection | Conveyors, counting |
Ultrasonic | Transparent and translucent object detection | Fill-level measurement |
PT100/PT1000 | High-accuracy temperature measurement | Ovens, process lines |
Pressure | Continuous pressure monitoring | Hydraulic, pneumatic systems |
Laser distance | Millimetre-level position measurement | Robotics, assembly |
Magnetic field | Cylinder piston position detection | Pneumatic actuators |
1. Inductive Proximity Sensor
What Is It?
Inductive proximity sensors detect the presence of metal objects by generating an electromagnetic field. They contain no moving parts, which means mechanical wear is virtually eliminated.
Why Is It on the List?
Detects different metals, such as steel, aluminium, and cast iron, with different sensitivity factors.
Commonly manufactured with IP67 and higher protection ratings.
Response times typically range from 0.3 ms to 1 ms across most models.
Low maintenance costs thanks to contactless operation.
Best Applications
Metal part transfer lines, CNC machine position control, and metal mould detection.
Limitations
They cannot detect non-metallic materials such as plastic, wood, or glass. Special high-temperature versions are required for applications above 150°C.
2. Capacitive Proximity Sensor
What Is It?
Capacitive proximity sensors detect changes in an electrostatic field, allowing them to detect virtually all types of materials, both metallic and non-metallic. Even water, granules, and powders can be detected.
Why Is It on the List?
Widely used in the food, pharmaceutical, and chemical industries.
Measures fill levels inside containers without physical contact.
Can be calibrated on-site using a sensitivity adjustment potentiometer.
Fills the gap left by inductive sensors when detecting non-metallic materials.
Best Applications
Product presence detection on packaging lines and fill-level monitoring in silos.
Limitations
Surface contamination and moisture can cause false triggering in sensitive applications. Their sensing range is generally shorter than that of inductive sensors.
3. Photoelectric Sensor
What Is It?
Photoelectric sensors operate using a light source and a receiver. They are available in three main configurations: through-beam, retro-reflective, and diffuse-reflective.
Why Is It on the List?
Sensing distances vary from 100 mm to 60 m, depending on the model.
Different models are available for detecting objects based on colour, transparency, and surface reflectivity.
IO-Link-compatible models can transmit diagnostic information to the PLC.
Thousands of objects per second can be counted in conveyor speed measurement and counting applications.
Best Applications
Bottle counting, label presence detection, and object detection on long conveyor belts.
Limitations
Glass and transparent objects may go undetected by reflective models. High concentrations of dust and smoke can weaken the signal.
4. Ultrasonic Sensor
What Is It?
Ultrasonic sensors calculate distance by measuring the time it takes for sound waves to travel to an object and return. Their performance is not affected by an object's colour, surface texture, or transparency.
Why Is It on the List?
Reliably detects transparent objects such as glass, plastic, and liquid surfaces.
Typical sensing ranges vary from 20 mm to 10 m.
Provides a non-contact solution for tank fill-level monitoring.
Supports continuous distance data transmission through analog outputs.
Best Applications
Liquid level measurement, transparent packaging inspection, and vehicle detection.
Limitations
Sound-absorbing surfaces, such as foam and cotton, weaken the reflected signal. Accuracy may also decrease in environments with very high noise levels.
5. Temperature Sensor (PT100/PT1000)
What Is It?
PT100 and PT1000 temperature sensors are RTD (Resistance Temperature Detector) sensing elements based on the relationship between platinum resistance and temperature. A PT100 sensor has a resistance of 100 ohms at 0°C.
Why Is It on the List?
The typical measurement range is between -200°C and +850°C.
Offers superior linearity and repeatability compared with thermocouples.
Three-wire and four-wire connection options minimise errors caused by lead resistance.
Widely used in food, pharmaceutical, and chemical processing applications.
Best Applications
Oven temperature control, process line temperature monitoring, and HVAC systems.
Limitations
There is a risk of mechanical damage in high-vibration environments. Response times are slower than those of thermocouples.
6. Pressure Sensor
What Is It?
Pressure sensors continuously measure gas or liquid pressure using piezoresistive or capacitive sensing principles. Industrial models typically operate with 4–20 mA analog outputs or digital IO-Link interfaces.
Why Is It on the List?
Real-time pressure monitoring in hydraulic and pneumatic circuits improves production safety.
Wide measurement ranges are available, from -1 bar to 1,000 bar.
Stainless steel diaphragms provide resistance to corrosion in demanding environments.
Monitor critical parameters in pneumatic presses and injection moulding machines.
Best Applications
Hydraulic presses, compressor control, and pipeline leak detection.
Limitations
High-viscosity fluids may cause delays in pressure transmission. Corrosion can occur if the diaphragm material is not compatible with the measured medium.
7. Laser Distance Sensor
What Is It?
Laser distance sensors measure position with millimetre-level accuracy by calculating the time of flight or phase difference of a reflected infrared laser beam. Robotic cells and precision assembly applications often require this level of accuracy.
Why Is It on the List?
Repeatability can reach as high as 0.1 mm.
Provides linear output at reference distances of up to 1,000 mm.
Analog and digital output options are compatible with most controllers.
A narrow beam diameter allows measurements on small target surfaces.
Best Applications
Robotic pick-and-place cells, part position verification on assembly lines, and quality control stations.
Limitations
Highly reflective or mirror-like surfaces can cause excessive reflection, resulting in unreadable measurements. Their cost is significantly higher than that of conventional proximity sensors.
8. Magnetic Field Sensor (Reed/Hall Effect)
What Is It?
Magnetic field sensors detect the position of a magnet mounted on a pneumatic cylinder piston without physical contact. Reed-type sensors use a mechanical contact, whereas Hall Effect sensors operate entirely electronically.
Why Is It on the List?
One of the most widely used solutions for forward and backward position feedback in pneumatic actuators.
Can be mounted directly into the cylinder groove, eliminating the need for additional cable routing.
Hall Effect types can withstand more than 10 million operating cycles.
Their compact form factor provides an advantage in applications with limited mounting space.
Best Applications
Pneumatic cylinder position feedback and automatic door or locking systems.
Limitations
Reed-type sensors contain mechanical contacts, which can reduce their service life under high-frequency switching. They may also generate false signals when used near strong magnetic fields.
How Do You Choose the Right Sensor?
The selection process starts by answering three questions: What needs to be detected (material type)? What are the operating conditions (temperature, humidity, IP rating)? And is the output signal compatible with the controller infrastructure?
For metal part detection, an inductive proximity sensor should be the first choice.
For non-metallic materials or food products, consider capacitive or photoelectric alternatives.
For applications requiring highly accurate position data, choose a laser distance sensor.
For pneumatic cylinder position feedback, a magnetic field sensor is the most cost-effective solution.
If operating conditions are harsh (washdown or chemical exposure), consider models with an IP69K rating.
Özdisan Elektronik provides electronic component supply and application support for automation systems. To receive technical assistance with sensor selection, visit the FAE and R&D Support page.
Frequently Asked Questions
Which sensor is most commonly used in industrial automation?
Inductive proximity sensors are among the most widely used sensor types in metal processing and assembly lines. They require no mechanical maintenance, typically offer IP67 protection, and have response times below 1 ms. However, they can only detect metallic materials.
Why is the IP protection rating important when selecting a sensor?
The IP protection rating defines a sensor's resistance to dust and water ingress. IP69K is generally required in environments involving industrial washdown, while IP67 is considered the minimum requirement in standard factory environments. Sensors with lower IP ratings can fail quickly under these conditions.
What is the difference between analog and digital outputs?
Analog outputs (4–20 mA or 0–10 V) are used to measure continuously varying values, such as distance or pressure. Digital outputs (PNP, NPN) transmit two-state information, such as object present or absent. IO-Link supports both types of communication and also provides diagnostic data.
When should you choose PT100 over a thermocouple?
PT100 sensors are suitable for applications requiring high accuracy and repeatability, typically between -200°C and +600°C. Thermocouples are preferable at temperatures above 600°C or in environments where very rapid temperature changes need to be monitored. Most food and pharmaceutical processes are managed using PT100 sensors.
When should an ultrasonic sensor be preferred over a photoelectric sensor?
Ultrasonic sensors provide more reliable results when detecting transparent, reflective, or irregularly shaped objects. Photoelectric sensors may struggle with these surfaces because light can pass through them or scatter in unpredictable ways
