VEGA D84 Hydrostatic pressure transmitter - Manual (Page 40)

40 Pressure transmitter D84
Diagnostics
6 Diagnostics
Maintenance
The pressure transmitter D84 is maintenance
free.
Should dismounting of the pressure transmit-
ter (e.g. for vessel cleaning) be necessary,
we recommend the use of new seals. Use
only original seals from VEGA.
Remedying faults
Through continuous self-monitoring, series 80
pressure transmitters offer maximum
reliability. However, if faults occur, please
check the following before removing the
pressure transmitter:
- the atmospheric pressure compensation
(only with gauge pressure measuring
ranges),
- the electrical connections.
Checking atmospheric pressure compen-
sation
First of all, open the cover of the housing in
which the atmospheric breather facility
1) is
located. The displayed measured value must
not change. If, however, the displayed value
changes, the compensation of the atmos-
pheric pressure does not function correctly
and the measured value will be distorted.
Therefore check:
- the breather facility on the housing
- the external connection housing
VEGADIS 12
- the capillaries in the special housing.
Note:
The same atmospheric pressure must be
acting on the breather facility and the open
vessel.
Checking electrical connections
Pressure
transmitter
terminals
~
1 2 3
+
-
Voltage Current
Current
External
energy source
V mA
mA
1) It consists of a black plastic screwed insert with
integrated filter element.
Checking the voltage
- The terminal voltage on the pressure trans-
mitter must be at least 12 V DC.
- The terminal voltage on VEGADIS 12 must
be at least 12 V DC or 17 V DC (with dis-
play).
- The supply voltage for the pressure trans-
mitter through a VEGAMET signal condi-
tioning instrument must be approx.
18 V DC (on VBUS 25 V DC).
Checking the current
These values are only valid for pressure
transmitters with analogue signal transmis-
sion, not for pressure transmitters with digital
output signal (VBUS).
• Initial current with uncovered diaphragm of
the pressure transmitter: approx. 4 mA
(5 mA when operated on a VEGA signal
conditioning instrument)
• Measuring current during operation:
4 … 20 mA (5 … 19 mA when operated on
a VEGA signal conditioning instrument)
• Exceeding or falling short of the specified
measuring range: 20.5 mA or 3.8 mA
• Pressure transmitter defective or short-
circuit: current 22 mA or 3.6 mA