User Manual

82 VEGAPULS 42 and 44 – 4 … 20 mA
Connection to a VEGA signal conditioning
instrument
If you operate a HART
®
compatible sensor on
a VEGA signal conditioning instrument, you
have to connect the sensor via a resistor
(see following table) during HART
®
adjust-
ment in order to reach, together with the
internal resistance of the instruments, the
value of 250 Ohm required for the HART
®
instrument. An inherent system load resist-
ance allows a corresponding reduction of Rx.
VEGA signal conditioning instr. Rx
VEGAMET 513, 514, 515, 602 50 … 100 Ohm
VEGAMET 614 no additional
VEGADIS 371 resistor
required
VEGAMET 601 200 … 250 Ohm
VEGASEL 643 150 … 200 Ohm
VEGAMET 513 S4, 514 S4
515 S4, VEGALOG EA card 100 … 150 Ohm
Setup
Just connect the HART
®
handheld to the
signal cable, after connecting the sensor to
power supply.
Note:
If the resistance of the power supply is less
than 250 Ohm, a resistor must be connected
into the signal/connection loop during adjust-
ment.
The digital adjustment and communication
signals would otherwise be short-circuited
due to insufficient resistance of the supply
current source or the processing system,
and as a result, communication with the sen-
sor would not be ensured.
+
-
Ri ³ 250 W
250 W
+
-
Ri < 250 W
With any HART
®
handheld you can set up the
VEGAPULS 40K radar sensors like all other
HART
®
compatible sensors. A special DDD
(Data Device Description) is not necessary.
6.4 Adjustment with HART
®
handheld