Vega VEGACAL 69, Руководство по эксплуатации

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3 Product description
VEGACAL 69 • Two-wire 4 … 20 mA/HART
31178-EN-200929
3.2 Principle of operation
VEGACAL 69 is a level sensor for continuous level measurement of
liquids in non-conductive vessels or of corrosive liquids.
The double rod probe is fully insulated and highly resistant.
Probes and measured product 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 two probes are the capacitor plates. The measured product is
the dielectric. Due to the higher dielectric constant of the product
compared to air, the capacitance increases as the material gradually
covers the probe.
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