3 operation – VEGA VEGACAL 67 Foundation Fieldbus User Manual
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3 Product description
VEGACAL 67 • Foundation Fieldbus
31760-EN-130917
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 is the dielectric. Due to the higher dielectric constant of the
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.
Power is supplied via the H1 Fieldbus. A two-wire cable according to
Fieldbus specification serves as carrier of both power and digital data
for multiple sensors. This cable can be operated in two versions:
•
via an H1 interface card in the control system and additional power
supply
•
via a Linking device with HSE (High speed Ethernet) and addi-
tional power supply according to IEC 61158-2
The DD (Device Descriptions) and CFF (capability files) necessary
for planning and configuration of your FF (Foundation Fieldbus) com-
munication network are available in the download area of the VEGA
under "Services - Downloads - Software
- Foundation Fieldbus". The appropriate certificates are also available
there. A CD with the appropriate files and certificates can be ordered
via e-mail under [email protected] or by phone from one of the
VEGA agencies under the order number "DRIVER.S".
The backlight of the display and adjustment module is powered by the
sensor. Prerequisite is a certain level of operating voltage.
The data for power supply are specified in chapter "Technical data".
The optional heating requires its own operating voltage. You can find
details in the supplementary instructions manual "Heating for display
and adjustment module".
This function is generally not available for approved instruments.
3.3 Operation
The instrument can be adjusted with the following adjustment media:
Power supply and bus
communication
DD/CFF