- LMC point level sensor
- Technology
Technology
Impedance spectroscopy
Deposits and foam often make reliable level detection difficult. The impedance spectroscopy technology measures the electric and magnetic field strength at multiple frequencies between 50…200 MHz range. Each medium creates a unique signature profile across this high frequency spectrum sweep. At each point, three measurements are made:
- Attenuation (dampening) of the electromagnetic field
- Conductance of the electric field (ability to conduct an electric current)
- Permittivity (ability to polarize particles) of the magnetic field
When the medium is present, these measurements match the profile. With no medium present or only residue present, the measurements do not match. When the measured profile falls in the green switching zone, the output of the sensor changes state.
No media present: The image above shows the situation with no media covering the sensor tip. There is low attenuation, low conductivity and low permittivity. The signature profile is outside of the switching zone.
Media present: This next image shows the profile when media is present on the tip. Attenuation, conductivity and permittivity are all high and the measured profile is within the switching zone. The output changes state.
Residue present: When only residue is covering the tip, conductivity and permittivity are high because there are traces of the medium present. But attenuation is low because the amount of medium is small. The profile is outside of the switching zone and the output does not change state.
Other media have different profiles. Using IO-Link, the medium process values can be evaluated and used to distinguish one material from another, i.e., oil vs. water, foam vs. liquid, etc.
Features:
- Suppression of residue build-up and foam.
- 316L stainless steel body for robustness.
All versions are programmable, but factory default settings are available for water-based media and oil-based / powder media.