Softing PROFIBUS Tester 5 - Page 48

PROFIBUS Tester 5 (BC-700-PB) - User Manual
48
Copyright 2016 Softing Industrial Automation GmbH
Connectors: Please specify, how many 12 MBit/s PROFIBUS-connectors exist in the respective cable
segment and enter the number in the segment configuration. The series inductance within the 12 MBit/
s PROFIBUS-connectors act like a delay element on the cable with respect to impulse reflectometry.
Every connector corresponds to approx. 50 cm cable length.
Devices: Please specify, how many PROFIBUS devices are connected to the respective cable segment
(Master, Slave, repeater; typ. not more than 32). The RS485-driver unit of each PROFIBUS-station acts
like a RC-cicuit (delay element) on the cable. In the context of impulse reflectometry this corresponds
to additional 20 cm cable length per device.
Thus, the combination consisting of connector plus device corresponds to approx. 70 cm cable length.
Example: A cable segment has approx. 50 m effective cable length and contains 20 PROFIBUS devices,
which are connected to the line by means of 12 MBit/s Sub-D type connectors. Without indicating the
number of connectors and devices the PROFIBUS Tester 5 (BC-700-PB) will detect a total cable segment
length of 64 meters, which corresponds to a systematic error of measurement of approx. 28 %. The
more precise you enter the number of connectors and devices into the segment configuration, the
more precise the length indication will be (cable segment length or distance to error).
Die Längenmessung im Kabelsegment ist optimiert für das Standard-PROFIBUS-Kabel Typ A. Die
ermittelten Segmentlängen unter Verwendung von Feldbuskabeln mit abweichenden Impedanzen
werden systematisch Messfehler aufweisen.