Dynacord H 2500 - Manual (Page 45)

PowerH SERIES
Owner’s Manual 45
Performance Specifications
According to the ISO 11898-2 standard, CAN-bus data transfer cabling has to be carried out using Twisted-
Pair cables with or without shielding providing a characteristic impedance of 120
Ω. Both ends of a CAN-
bus need to be terminated with 120 Ω termination-plugs. The maximum bus-length depends on the actual
data transfer rate, the kind of data transfer cable being used, as well as the total number of participants on
the bus. The following table shows the most essential requirements for CAN-networks consisting of up to
64 participants.
* With longer cables and many participants on the CAN-bus, termination resistors with higher impedance
than the specified 120
Ω are recommended to reduce the ohmic load of the interface drivers and therefore
the voltage drop between the two cable-ends.
The following table is meant for first assessment of necessary cable diameters for different bus lengths and
bus-participant numbers.
Additionally, the length of branch lines - for participants that are not directly connected to the CAN-bus - is
also of importance. For data transfer rates of up to 125 kbit/s, the maximum length of a single stub cable
should not exceed 2 meters. For higher bit rates a maximum length of only 0.3 meter is still permissible.
The entire length of all branch lines should not exceed 30 meters.
General Note:
• As long as only short distances (up to 10 meters) are concerned, common RJ-45 patch cables with a
characteristic impedance of 100
Ω (AWG 24 / AWG 26) can be used for the cabling inside of a rack
mounted system.
• The previously outlined guidelines for network cabling are mandatory as far as the rack mounted
shelve interconnection or fixed installations are involved.
Bus Length
(in m)
Data Transmission Cable
Termination (in Ω) Max. Data Transfer Rate
Resistance per Unit
Length
(in m Ω/m)
Cable Diameter
0...40 < 70
0,25...0,34 mm²
AWG23, AWG22
124
1000 kbit/s
at 40 m
40...300 < 60
0,34...0,6 mm²
AWG22, AWG20
127
500 kbit/s
at 100 m
300...600 < 40
0,5...0,6 mm²
AWG 20
150...300*
100 kbit/s
at 500 m
600...1000 < 26
0,75...0,8 mm²
AWG 18
150...300*
62,5 kbit/s
at 1000 m
Bus Length (in m)
Number of Units on the CAN-Bus
32 64 100
100 0,25 mm² / AWG24 0,34 mm² / AWG22 0,34 mm² / AWG22
250 0,34 mm² / AWG22 0,5 mm² / AWG20 0,5 mm² / AWG20
500 0,75 mm² / AWG18 0,75 mm² / AWG18 1,0 mm² / AWG17