Glossary · Sensors and measurement
Capacitive proximity sensor
Also known as: Capacitive proximity switch
German: Kapazitiver Näherungssensor
In industrial automation, a capacitive proximity sensor is a non-contact sensor that detects objects by the change they cause in the capacitance of its sensing field. It detects metals as well as non-metals such as plastics, wood, liquids and bulk materials.
- Sensors
- Standards
In one sentence
A capacitive proximity sensor detects metallic and non-metallic objects without contact through the change in capacitance of its sensing field.
Example
A capacitive proximity sensor mounted on the outside of a plastic hopper signals when the granulate falls below the sensor level.
How it applies
- Engineering: The switching distance depends on the dielectric properties of the target. Datasheets state a rated switching distance for a standard target; materials with a lower dielectric constant are detected at a shorter distance.
- Commissioning: Most capacitive proximity sensors have a sensitivity adjustment. Set it with the real material and container wall, and check that build-up or moisture on the sensor face does not cause false signals.
- Maintenance: Deposits on the sensing face can keep the output switched. Include cleaning and a function check in the maintenance plan.
- Documentation: Describe the target material and the set sensitivity. Operators need to know that a changed material can change the switching point.
Capacitive vs. inductive proximity sensor
An Inductive proximity sensor detects only metal and is largely insensitive to dirt and non-metallic materials. A capacitive proximity sensor detects almost any material, which makes it useful for level detection but also more sensitive to deposits and humidity.