Commissioning Hardware PolyGard
®
DGC- 05
Page 16
PolyGard
is
a
registered
trademark
of
MSR
GAINBDGC05_E_1206
Phone.:
0049(0)8531/9004-0
Fax:
0049(0)8531/9004-54
Specification subject to change without notice.
MSR-Electronic GmbH, Würdinger Str. 27, D 94060 Pocking
www.msr-electronic.de
Made in Germany
5.2
Check short-circuit / interruption / cable length of the bus leads
This procedure has to be executed for each single segment.
Disconnect the bus leads from pin 3 and pin 4 of the DGC- 05 central control.
Connect ohmmeter to the loose leads and measure the total loop resistance.
See fig. 15 Loop resistance.
The total loop resistance is calculated as follows:
R (total) = R (cable) + 560 Ohm
(terminating resistance)
R (cable) = 71 Ohm / km
(loop resistance)
(JY(St)Y 2x2x0,8LG)
R
(total)
=
< 560 Ohm
Short-circuit
Look for short-circuit in the field
R
(total)
=
infinite
Cable
interruption Look
for
cable
interruption
in
the
field
R
(total)
=
> 560 Ohm < 640 Ohm
Cable is OK
The cable length can be calculated in a sufficiently exact way according to the following formula.
Total cable length (km) = (R
(total
)
– 560 Ohm) / 71 Ohm
If the field bus cable is OK, reconnect it to the central control.
Fig. 15 Loop resistance
1
1
1
1
1
1
X4
DT-05
X4
DT-05
X4
DT-05
X4
DT-05
X4
DT-05
2
2
2
2
2
2
3
4
5
7
6
6
6
6
6
6
8
7
7
7
7
7
560 R
OHM
DGC-05
central control
