VEGA VEGABAR 21 - Manual (Page 4)

4 VEGABAR 21
Product description
1 Product description
1.1 Function and configuration
VEGABAR 21 is an efficient pressure trans-
mitter with isolating system for process pres-
sure measurement and hydrostatic level
measurement. The hydrostatic pressure of
the medium acts on the separating dia-
phragm of the isolating system and is trans-
ferred via the isolating liquid to a ceramic-
capacitive measuring cell CERTEC
® . The
pressure on this measuring cell effects a
capacitance change within the measuring
cell. This capacitance change is detected by
an ASIC (Application specific integrated
circuit) and converted by an integral oscilla-
tor with microcomputer into a pressure pro-
portional signal. The exact, digital processing
of measured data with highest resolution
ensures perfect technical data.
Isolating systems are used to protect the
measuring cell against aggressive products
and high temperatures. Due to the suitable
selection of isolating liquid and diaphragm
material, systems with a temperature resist-
ance up to 400°C are possible.
The oscillator is powered by a separate
VEGA-signal conditioning instrument, a stabi-
lised power supply unit or a DCS (active
input). After the adjustment, a standardised
current signal 4 … 20 mA is available which
can be displayed (e.g. in DCS-systems) or
further processed.
Two versions are available for adjustment:
- adjustment module directly on VEGABAR
- adjustment module in external housing
(VEGADIS 10)
1.2 Self-monitoring
Important electronics components are
checked on their function and internal param-
eters such as sensor value, temperature and
operating voltage are monitored to increase
the reliability.
VEGABAR 21 with ceramic CERTEC ® -meas-
uring cell offers the advantage of a continu-
ous self-monitoring. Measuring and reference
capacitance of the measuring cell are in a
defined relation over the complete measuring
range. Each deviation from these data is a
reliable indicator for a malfunction of the
measuring cell.
If during these routines failures or malfunc-
tions are detected, a fault signal is triggered
via the 4 … 20 mA-output (current jump to
3,6 mA or 22 mA).