Definition
Capacitive sensors evaluate the change in capacity caused by an object entering the electric field of the capacitor. This means that they can sense not only conductive but also nonconductive materials with permittivity εr large enough (e.g. glass, fluids, bulk solids).
|
Reducing agent for different materials |
|||
|
Air |
0 |
Plexiglass |
0,29 |
|
Teflon |
0,2 |
Glass |
0,4 |
|
Oil |
0,25 |
Alcohol |
0,72 |
|
PVC |
0,27 |
Water |
1 |
|
Polypropylene |
0,26 |
Steel |
1 |
|
Polyethylene |
0,26 |
|
|
Sensors affect:
· Temperature, because εr is temperature dependent.
· Humidity
· For absorbent materials such as wood, the sensitivity of the sensor and the moisture content of the material are affected.
The main application for these sensors is the sensing of bulk materials and liquids. An advantage can be the ability to scan across the container wall.
