Installing Dräger Polytron 7500
Page 10 of 72 Pages
9023927 - 2nd edition - May 2007
– Connecting to the central unit with individual power supplies:
1)
IMPORTANT: star-shaped ground system (no ground loops).
R
X
corresponds to line resistance R
line
– Connecting to a HART Multidrop-capable central
To ensure that the unit operates as intended, the impedance of the 4 to 20 mA signal
loop must not exceed 500 Ohm and must be between 230 and 500 Ohm for HART-
compatible "smart" loops. The conductors of the power supply must have a suffi-
ciently low resistance to ensure that the supply voltage of the unit is correct.
●
Each unit must first be put into service separately.
Use the menu item "Polling Address" to assign a different polling address in the
range "1" to "15" to each Polytron 7500, which is to be connected to the multidrop
cable. It is best to assign sequential polling addresses, starting with "1".
●
Depending on the supply unit, up to 8 Polytron 7500s can be connected to a line.
Multidrop installation with HART communication and individual power supplies:
R
shunt
= 230 ... 500
Ω
Multidrop installation with HART communication and a (central) power supply:
R
cable
(pro wire) < U – 15 V
Ω
/ n x 0.8 [
Ω
]
n = actual number of units in feed unit
U = output voltage in V of the feed unit with an output current of
n x 0.4 A
R
shunt
= 230 ... 500
Ω
+
–
+
–
R
shunt
Pyrolyzer 1
Central unit
Pyrolyzer 2
+
–
R
shunt
R
X
0462392
7_1_en.eps
R
X
0 V
4...20
+2
4 V
0 V
4...20
+2
4 V
1)
1)
