Technische Alternative CAN-EZ3, Общая информация, Установка и подключение, Основные функции

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Installation and connection – CAN bus
18
Cable selection and network topology
Screened twisted pairs have proven useful in CANopen networks. These are cables with twisted
pairs of conductors and a shared external screen. Such cables are relatively resistant to EMC inter -
ference and can still carry 50 kbit/s for up to 1000 m. The CANopen recommendations (CiA DR 303-
1) for cable cross-sections are given in the table below.
The maximum cable length also depends on the number of nodes [n] linked with the bus cable and
the cable cross-section [mm²].
Bus rate
In the CAN bus / CAN settings menu of the UVR16x2, the bus rate can be set to between 5 and 500
kbit/s, whereby lower bus rates enable longer cable networks. However, in this case, the cable cross-
section must be increased accordingly.
The standard bus rate of the CAN network is 50 kbit/s (50 kBaud), which is specified for many CAN
bus devices.
Important: All devices in the CAN bus network must have the same transfer rate in order to be able
to communicate with each other.
Recommendations
A 2x2-pole, screened twisted pair (twist CAN-L with CAN-H or +12 V with GND) with a cable cross -
section of at least 0.5 mm² and a conductor-to-conductor capacity of no more than 60 pF/m and a
nominal impedance of 120 ohms. The standard bus speed of the UVR16x2 is 50 kbit/s. This recom -
mendation corresponds, for example, to cable type Unitronic®-BUS CAN 2x2x0.5 supplied by Lapp
Kabel for permanent installation in buildings or conduits. Theoretically this would enable a bus
length of approx. 500 m to guarantee reliable transmission.
For
direct routing underground, earth cable 2x2x0.5 mm² supplied by HELUKABEL, part no. 804269,
or earth cable 2x2x0.75 mm² supplied by Faber Kabel, part no. 101465, would be suitable.
Bus length
[m]
Resistance in terms
of length [mΩ/m]
Cross-section
[mm
2
]
0...40 70 0,25...0,34
40...300 < 60 0,34...0,60
300...600 < 40 0,50...0,60
600...1000 < 26 0,75...0,80
Cable cross-section
[mm
2
]
Maximum length [m]
n=32 n=63
0,25 200 170
0,50 360 310
0,75 550 470
Bus rate [kbit/s] Maximum permissible total bus length [m]
5 10.000
10 5.000
20 2.500
50 (standard) 1.000
125 400
250 200
500 100