Flexim FLUXUS G608 - Page 39

6 Installation of FLUXUS G601 FLUXUS G60x
UMFLUXUS_G6V4-2EN, 2011-03-29 39
If the polarity of the current source is inversed, only the sign of the measured current will
change.
An external voltage source U
ext
is necessary. It must provide a current of min. 20 mA and
• supply sufficient power for the energy requirements of the passive current source and
• cover the voltage drop at the input resistor (1 V at 20 mA) and
• cover all other voltage drops (e.g. cable resistance) in the circuit.
Tab. 6.3: Connection of a passive current source
input transmitter external circuits note
internal circuits connection
passive
current input

+
-
short circuit current:
max. 40 mA
example: A passive current source (e.g. a pressure sensor) is to be connected to a
passive current input.
Technical data of the pressure sensor:
U
S
= 11...30 V DC
I
a
= 4...20 mA (I
a max
= 22 mA)
U
ext
required for the operation of the passive pressure sensor is:
U
ext min
=
=
=
U
S min
+ I
a max
· R
i
+ I
a max
· R
c
11 V + 22 mA · 50 Ω + 20 mA · 2 Ω
12.14 V
U
ext max
=
=
U
S max
30 V
U
S
- operating voltage of the pressure sensor
I
a
- output current
R
i
- input resistance
R
c
- cable resistance
+
-
V
R
i
U
ext