VEGA VEGAPULS 41 4 … 20 mA; HART compact sensor - Manual (Page 35)

VEGAPULS 41 – 4 … 20 mA 35
26620-EN-041227
2
4 … 20 mA
2
2
2
4
Electrical connection
Measuring system with VEGAPULS 41 via separator in Ex areas on active
PLC (Ex ia)
• Two-wire technology (loop powered), power supply via the signal line of the PLC; output
signal 4 … 20 mA (passive).
• Separator transfers the non intrinsically safe PLC circuit to the intrinsically safe circuit, so
that the sensor can be used in Ex zone 1 or Ex zone 0.
• Optional external indicating instrument with analogue and digital display (can be mounted
up to 25 m away from the sensor).
• Adjustment with PC, HART ® handheld or adjustment module MINICOM (can be plugged into
the sensor or into the external indicating instrument VEGADIS 50).
HART ® handheld
Ex area Non Ex area
Separator (e.g. Stahl)
(see "6.2 Approvals“)
VEGA-
CONNECT
VEGADIS 50
passive 2)
1 )
PLC (active)
1) If the resistance of the processing systems
connected to the 4 … 20 mA signal output is less
than 250
Ω, a resistor must be connected to the
connection cable during adjustment to get a loop
resistance of 250
Ω.
The digital adjustment signal would otherwise be
severely damped or short-circuited due to
insufficient resistance of the connected
processing system. Digital communication with the
PC would not be ensured.
Zone 0 or
Zone 1
EEx ia
2) 4 … 20 mA passive means that the sensor or the
PLC consumes a level-dependent current of
4 … 20 mA. The PLC reacts electrically like a
varying resistor (consumer) to the PLC. The PLC
operates actively, i.e. as current or voltage
source.