Finding the right sensor: selection & comparison
Choosing the right sensor determines the reliability and service life of a plant. This guide walks you through the key selection criteria and compares the common measuring principles, vendor-neutral, so the solution fits your requirements rather than a single manufacturer's range.
The five most important selection criteria
First, the material of the object to detect: only metal points to inductive sensors, any material to capacitive or optical ones. Second, the required distance or measuring range. Third, the ambient conditions: temperature, humidity, contamination and the necessary IP rating. Fourth, the output signal, which has to match the controller (analogue, digital or IO-Link). Fifth, housing and mounting, such as cylindrical M8/M12/M18 or a rectangular housing.
Inductive vs. capacitive vs. optical
Inductive sensors are the most rugged choice, but limited to metal and with a short switching distance. Capacitive sensors detect almost any material and suit level measurement, but react more sensitively to contamination and moisture. Optical sensors bridge long distances and detect very small objects, yet are more vulnerable to dirt on the lens and to highly glossy or transparent surfaces. For exactly those difficult surfaces, ultrasonic sensors are the better choice.
| Principle | Material | Range | Strength |
|---|---|---|---|
| Inductive | metal only | short | rugged, fast |
| Capacitive | almost any | short to medium | level |
| Optical | almost any | long | small objects |
| Ultrasonic | almost any | medium | glossy, transparent |
Judging the switching distance correctly
The stated nominal switching distance applies to a standardised target: for inductive sensors, a steel plate. Other metals reduce the real switching distance via a correction factor: stainless steel, aluminium or copper give noticeably shorter ranges. Always allow a safety margin and check the real switching distance for your specific material.
Checklist for sensor selection
Before ordering, clarify six points: the object material, the required switching or measuring distance, the desired output signal, the housing and connection, the required IP rating, and any special ambient factors such as temperature or cleaning method. Once these are answered, the choice usually narrows to a handful of models.
Unsure? How we help
Describe your application in your own words. Our AI advisor suggests suitable sensors from our product range. For complex cases, arrange a personal consultation. For in-depth basics, see sensor basics.