Vega VEGABAR 86 Operating Instructions Manual page 9

Measuring system pres-
sure
Measuring system tem-
perature
Pressure types
Seal concept
VEGABAR 86 • 4 ... 20 mA
The sensor element is the CERTEC
ceramic diaphragm. The process pressure deflects the ceramic
diaphragm and causes a capacitance change in the measuring cell.
This capacitance change is converted into an electrical signal and
outputted as measured value via the output signal.
The measuring cell is available in two sizes:
•
CERTEC (ø 28 mm) with sensor 32 mm
®
•
Mini-CERTEC (ø 17.5 mm) with sensor 22 mm
®
A temperature sensor in the ceramic diaphragm of the CERTEC
on the ceramic base of the Mini-CERTEC
actual process temperature. The temperature value is output via:
•
The display and adjustment module
•
The current output or the additional current output
•
The digital signal output
Even extreme jumps in process temperature are immediately de-
tected by the CERTEC
diaphragm are compared with those on the ceramic base body. Within
a few measuring cycles, the intelligent sensor electronics compen-
sates for otherwise unavoidable measurement deviations caused by
temperature shocks in the range. Depending on the adjusted damp-
ing, these cause only slight and brief changes in the output signal.
The measuring cell design depends on the selected pressure type.
Relative pressure: the measuring cell is open to the atmosphere.
The ambient pressure is detected in the measuring cell and compen-
sated. It thus has no influence on the measured value.
Absolute pressure: the measuring cell contains vacuum and is
encapsulated. The ambient pressure is not compensated and does
hence influence the measured value.
Relative pressure, climate-compensated: the measuring cell is
evacuated and encapsulated. The ambient pressure is detected
through a reference sensor in the electronics and compensated. It
thus has no influence on the measured value.
The following illustration shows the installation of the ceramic measur-
ing cell in the sensor as well as the sealing concept.
At temperatures above 100 °C the function is automatically deactivated, at
1)
temperatures below 95 °C it is automatically reactivated.
measuring cell with robust
®
measuring cell detects the
®
measuring cell. The values in the ceramic
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3 Product description
or
®
1)
9