Sep 18, 2026Buying Guides
Inductive vs Capacitive Proximity Sensors: A Practical Selection Guide
Metal or non-metal target? How inductive, capacitive and magnetic cylinder sensors differ, and how to pick the right proximity principle.
Two contactless principles, two jobs
Proximity sensors detect objects without contact. Inductive sensors respond to metal; capacitive sensors respond to almost anything that changes an electric field, including plastic, liquids and granulate. Knowing which principle matches the target is the whole selection decision.
Inductive: the metal detector of automation
An inductive sensor generates an electromagnetic field at its face. Metal entering the field damps an internal oscillator and the output switches. The detection is contactless, wear-free and insensitive to dust, oil and vibration. Standard tasks - end-position monitoring on cylinders, metal part counting, cam and gear sensing - are handled by families such as the M12-threaded SICK IME12-08NPSZC0S or the miniature M8-format SICK IME08-02BPSZT0K.
Sensing range and target material
The nominal range of an inductive sensor applies to mild steel. Stainless steel, aluminum and copper reduce the effective distance, sometimes substantially. Flush or non-flush mounting also changes the range, because surrounding metal pulls the field. Design with these two factors and the sensor will behave exactly as the datasheet promises.
Capacitive: seeing the non-metallic world
Capacitive sensors evaluate changes in an electrostatic field, so they detect plastics, wood, glass, liquids and powders. The classic application is level detection through a non-metallic tank wall, or presence detection of packaging on a line. The M18-format SICK CM18-08BNP-EW1 and the larger M30-format SICK CM30-25NPP-EC1 cover these tasks with adjustable sensitivity.
Magnetic cylinder sensors: position inside the actuator
Pneumatic cylinders carry their own sensing solution: magnetic position sensors clamped into the cylinder slot detect the piston magnet through the aluminum wall. T-slot variants such as the SICK MZT7-03VPS-KP0 and SICK MZT8-03VPS-KP0, the C-slot model SICK MZ2Q-CSSPSKU0, and the compact SICK TMM22E-PKH060S55 provide end-position and mid-stroke signals with no mechanical wear at all.
Quick selection checklist
- Metal target: inductive - choose the range class and flush or non-flush mounting.
- Non-metallic target or level through a wall: capacitive.
- Piston position in a pneumatic cylinder: magnetic slot sensor.
- Harsh environment: inductive wins on robustness; capacitive needs a clean active face.
Frequently Asked Questions
Can an inductive sensor detect plastic bottles?
No - inductive technology responds only to metals. Use a capacitive sensor for plastics and liquids.
Why does my capacitive sensor trigger without a target?
Usually the sensitivity is set too high and the sensor sees the mounting bracket or the wall behind the target. Reduce sensitivity and keep the active face clean.
Do magnetic cylinder sensors need a special piston?
The piston must carry a magnet, which is standard on sensor-ready pneumatic cylinders.
Next steps
Browse inductive, capacitive and magnetic families in our proximity sensors category and match the principle to your target in minutes.
