Capacitive sensors detect any material with or without contact. With ifm’s capacitive proximity sensors, the user can adjust the sensitivity to detect liquids or solids even through non-metallic tanks or vessels.
A capacitor consisting of two plates generates an electrical between the plates when supplied with power. Any material entering this field changes the capacitance on these plates.
A capacitor can also consist of a single plate. In this case, the second “plate” is earth ground.
All capacitive sensors have the same basic components:
In the case of capacitive sensors, the basic sensing element is a single plate capacitor where the connection is earth-grounded. When a target is moved into the sensing field, the capacitance changes and the output is switched.
Our datasheets specify 3 different detection distances.
|Sensing range (mm)||4|
|Real sening range Sr (mm)||4 ± 10%|
|Operating distance (mm)||0...3.25|
Less common than target size is target shape. It is difficult to provide a correction factor based on shape, so testing should be conducted when the sensing distance is critical.
Finally, the major contributor to the sensing range influence is the dielectric constant of the target. With capacitive level sensors, the higher the dielectric constant, the easier the material is to detect. As a general rule of thumb, if the dielectric constant is > 2, the material should be detectable. The following is a general guideline of dielectric constants for some materials. This information is provided for reference only.
The image shows the general influence of shape.
For successful level detection using capacitive sensors, make sure:
|High and low level particulate detection||High and low level liquid detection|