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Guide

Inductive, capacitive or photoelectric sensor: how to choose

Choose between inductive, capacitive and photoelectric sensors by target material, sensing distance, environment and output type.

  • 5 min read
  • Updated

What each type detects

  • Inductive: metal targets only. The rated sensing distance applies to steel; other metals such as aluminium or copper are detected at a shorter distance.
  • Capacitive: metals, plastics, liquids, powders and grain. Sensitivity is often adjustable and the sensor can be affected by moisture or build-up.
  • Photoelectric: any object that interrupts or reflects light. Types include through-beam, retro-reflective and diffuse, with ranges from millimetres to many metres.

How to choose

  1. Identify the target material, size and colour or surface.
  2. Choose the sensing distance with a safety margin, since the real operating distance should be below the rated one.
  3. Check the environment: dust, water, oil, temperature, vibration and washdown.
  4. Select the output: PNP (switches positive) or NPN (switches ground), and normally open or normally closed, to match your PLC input.
  5. Pick the housing and connection, such as threaded M12 or M18 barrel with an M12 connector.

Frequently asked questions

What is the difference between PNP and NPN?

A PNP output switches the positive supply to the load, and an NPN output switches the load to ground. Your PLC input type determines which you need.

Can an inductive sensor detect plastic?

No. Inductive sensors respond to metal. Use a capacitive or photoelectric sensor for plastic.

What is a through-beam sensor?

It uses a separate emitter and receiver facing each other. The object is detected when it breaks the beam, and this type gives the longest range and most reliable detection.

This guide is general engineering guidance. Always confirm part-specific details, ratings and compatibility against the manufacturer’s datasheet. We confirm price, stock and specifications for the exact part in a written quotation. See the glossary for the terms used here.