9
3 Product description
VEGACAL 64 • Two-wire 4 … 20 mA/HART
30030-EN-200929
3.2 Principle of operation
The VEGACAL 64 is a level sensor for conductive and non-conductive
liquids.
The rod probe is fully insulated and suitable for all viscous and adhe-
sive products.
Probe, measured product and vessel wall form an electrical capacitor.
The capacitance is influenced by three main factors.
1
2
3
Fig. 3: Functional principle - Plate capacitor
1 Distance between the electrode surfaces
2 Size of the electrode surfaces
3 Type of dielectric between the electrodes
The probe and the vessel wall are the capacitor plates. The measured
product and the insulation are the dielectric. Due to the higher dielec-
tric constant of the insulation and the conductive product compared to
air, the capacitance increases as the probe is gradually covered.
The capacitance as well as the resistance change are converted by
the electronics module into a level-proportional signal.
4 … 20 mA/HART two-wire electronics for voltage supply and meas-
ured value transmission on the same cable.
The supply voltage range can differ depending on the instrument
version.
The data for power supply are specified in chapter "
Technical data
".
The backlight of the display and adjustment module is powered by the
sensor. The prerequisite for this is a supply voltage at a certain level.
The exact voltage specifications are stated in chapter "
Technical
data
".
The optional heating requires its own voltage supply. You can find
further details in the supplementary instructions manual "
Heating for
display and adjustment module
".
This function is generally not available for approved instruments.
3.3 Adjustment
The instrument can be adjusted with the following adjustment media:
•
With the display and adjustment module
Application area
Functional principle
Voltage supply
