Type büS

Best practice instructions

32

12

BEST PRACTICE INSTRUCTIONS

12.1

Termination resistor

Termination resistors are located on each side of the trunk line. Each resistor has a resistance of approx.

120 Ω. Therefore, a network with a termination resistor at both ends has an impedance of 60 Ω. Resistors

are available as a male or female M12 connector. Additionally, a chip resistor for ME43 and valve island

Type 8652 is available.

12.2

Signal reflections

There might be more than one reason for signal reflections in a network. This depends on the number of

devices, the baud rate, the amount of process data, the position of the termination resistors and the posi-

tion of the measurement port.

Massive signal reflections occur if the position of the termination resistors is not selected correctly.

12.3

Passive junction box

Passive junction boxes are used for the distribution of devices that are close to each other. In a network

with a passive junction box, it is important to determine the longest distance between two devices and to

place the termination resistor there. In this case, it is not recommended to place these resistors on the trunk

line.

12.4

Diagnostic port

In a büS network, one diagnostic port should be placed in one plant. It is used for fast access with the

Bürkert Communicator or also a third-party tool, e.g. GEMAC CAN Bus Tester 2.

12.5

Baud rate

The default baud rate of all Bürkert devices is 500 kbit/s. In the case of a poor measurement result, it is

possible to reduce the baud rate to 250 kbit/s or 125 kbit/s. Therefore, longer cables can be used in the

network.

Please note that the total time of a firmware update increases when the baud rate is reduced to a lower

communication speed.

12.6

büS stick

The büS stick is a USB-to-CAN converter and is connected to a laptop/PC with the Bürkert Communicator.

It is used for the diagnostics, start-up and parameterisation of devices.

12.7

Stub lines

The total length of stub lines in the entire network should be reduced as much as possible. It is impossible

to calculate exactly the impact that a one metre stub line has on reducing the signal quality in percentage

terms.

12.8

Bus load

The maximum bus load is 40%. The specific bus load of a device is specified in the communication data

sheet. To calculate the total bus load, sum up the values from the communication data sheet for all devices.