"The all-rounders …"
With capacitive sensors by Baumer you solve almost any application.
Capacitive sensors can detect metallic, non-metallic, transparent, opaque, liquid and solid, conductive and non-conductive substances reliably without the need for contact. They are thus well suited to detect a diverse objects or also bulk goods and liquids.
These "all-rounders" are available in a large number of different designs and versions, and can also be implemented in very flat and space-saving designs.
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Portfolio
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Level detection
- Detection with material contact or without
- Detection possible through a container
- Suitable for liquids, granules and bulk goods
Sensors for special applications
- Sensors for fill levels of soiled media
- Use at very high temperatures
- Optimized housing design prevents dirt from sticking
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Object detection
- Surface-independent measuring principle: Color and textures play no role
- Flat shape allows space-saving installation
- Detection possible for the smallest objects
Smart installation solution
- Flexible installation with unique mounting frame
- Sensor easily snaps in and out without tools
- Cascading several sensors is possible
Application areas
- Liquid level monitoring of return flow tanks in laboratory automation
- Ink level detection in offset printing machines
- Wafer detection in solar cell manufacturing facilities
- Presence detection of plastic containers
Key features
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- Contactless detection of liquids and objects
- Measurement of fill levels possible through container walls
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- Robust, dirt-resistant design
- Highly sensitive to water and water-based media
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- Reliable detection of conductive and non-conductive materials
- Exceedingly flat designs possible
Special feature
Through our production and development know-how acquired over many years, and through our proximity to the market, we are in a position not only to offer our standard portfolio but also to develop application-optimized solutions and innovations as well as unique mounting concepts.
Technology
Function
The capacitive sensor basically functions like an open capacitor. An electrical field is formed between the measuring electrode and the GND electrode. If a material with a dielectric constant εr greater than air enters the electrical field, the capacity of the field increases depending on the εr of this material. The electronics measure this capacity increase, the generated signal is conditioned during subsequent signal processing and causes output switching at a corresponding magnitude.
Sensors with GND electrode
These sensors can be flush-mounted with the sensing face in a material. Because the measuring field of these sensors extends from the measuring to the integrated GND electrode, a defined measuring field is created. They are particularly suitable for detecting non-conductive materials such as oils, glass, wood or plastics, but can also detect conductive materials just as well. To prevent undesired switching and moisture on the sensor surface, a compensating electrode was integrated to suppress undesired objects.
Sensors without a GND electrode
Generally these sensors cannot be flush mounted. Since they do not have a GND electrode, the object to be detected performs the function of a GND electrode. Sensors without a GND electrode feature low sensitivity to soiling and condensation and are suitable especially for level tasks. To achieve long sensing distances, the medium to be detected should be conductive and optimally grounded.
Detectable media
Dielectric constant
Capacitive sensors detect conductive as well as non-conductive media with a dielectric constant εr > 1. The dielectric constant εr (also relative permittivity or inductive capacitance) of a material indicates how many times greater the electric flux density will become if instead of vacuum (air) the corresponding material enters the measuring field.
Conductive media
Conductive media typically has an electrical conductivity > 20 μS/cm. Conductive material can easily be detected by all sensor types whether they have a GND electrode or not. In conductive media the dielectric constant is irrelevant for the sensing distance. The sensing distance is influenced by the size of the object and its grounding.
Conductive media include:
- Water
- Blood
- Ink
- Milk
- Acetone
- MetalsNon-conductive media
Non-conductive media typically has an electrical conductivity < 20 μS/cm. In general sensors with a GND electrode are recommended for non-conductive media. If a non-conductive object is moved into the sensor field, the field increases depending on the dielectric constant and the size of the material to be detected, increasing the capacity of the measuring field. The lower εr is, the harder it is to detect the medium. Generally it can be said that e.g. for plastics with εr = 3 the effective sensing distance Sr corresponds to approximately 50% of the nominal sensing distance Sn.
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