Vega VEGAPULS 68 - Principle of operation

11
Electronics - 4 … 20 mA/HART - two-wire
Radar - Level measurement in bulk solids
29427-EN-160312
7 Electronics - 4 … 20 mA/HART - two-wire
Congurationoftheelectronics
The plug-in electronics is mounted in the electronics compartment of the
instrument and can be exchanged by the user when servicing is required.
The electronics is completely encapsulated to protect against vibration
and moisture.
The terminals for voltage supply as well as the contact pins with I²C
interface for parameter adjustment are located on the upper side of the
electronics. In the double-chamber housing, the terminals are located in
the separate terminal compartment.
Voltage supply
Power supply and current signal are carried on the same two-wire cable.
The operating voltage can dier depending on the instrument version.
You can nd the data of the voltage supply in chapter "Technical data" in
the operating instructions manual of the respective instrument.
Provide a reliable separation between the supply circuit and the mains
circuits according to DIN EN 61140 VDE 0140-1.
Specications of the voltage supply:
•
Operating voltage
– 9.6 … 35 V DC
– 12 … 35 V DC
•
Permissible residual ripple - Non-Ex, Ex-ia instrument
– for 9.6 V< U
N
< 14 V: ≤ 0.7 V
e
(16 … 400 Hz)
– for 18 V< U
N
< 35 V: ≤ 1.0 V
e
(16 … 400 Hz)
Keep in mind the following additional factors that inuence the operating
voltage:
•
Lower output voltage of the power supply unit under nominal load
(e.g. with a sensor current of 20.5 mA or 22 mA in case of fault)
•
Inuence of additional instruments in the circuit (see load values in
chapter "Technical data" of the operating instructions of the respec-
tive instrument)
Connectioncable
The instrument is connected with standard two-wire cable without
screen. If electromagnetic interference is expected which is above the
test values of EN 61326-1 for industrial areas, screened cable should be
used.
We generally recommend the use of screened cable for HART multidrop
mode.
Cablescreeningandgrounding
If screened cable is required, we recommend connecting the cable
screen on both ends to ground potential. In the sensor, the screen should
be connected directly to the internal ground terminal. The ground terminal
on the outside of the housing must be connected to the ground potential
(with low impedance).
Connection
Singlechamberhousing
5
1
2
+
( )
(-)
678
4...20mA
2
3
4
1
Fig. 20: Electronics and terminal compartment, single chamber housing
1 Voltage supply/Signal output
2 For display and adjustment module or interface adapter
3 For external display and adjustment unit
4 Ground terminal for connection of the cable screen
Doublechamberhousing
4...20mA
2
3
1
2
+
( )
(-)
1
Fig. 21: Terminal compartment, double chamber housing
1 Voltage supply/Signal output
2 For display and adjustment module or interface adapter
3 Ground terminal for connection of the cable screen