ABB AC 800M

Section 5 Maintenance FOUNDATION Fieldbus – CI852
3BSE 027 941 R301 133
The network
problem is
proving very
difficult to solve
(continued).
Use an oscilloscope to check the communication signals for
abnormalities.
• The oscilloscope must be of differential or battery
operated type.
• Probes must have a minimum of 1 MOhm input
resistance, and less than 1000 pF input capacitance.
Disconnect sections of the network, including the Ethernet port
via the PM8xx processor unit, until it is reduced to a size that
functions correctly.
• A hand-held fieldbus master unit should be used to make
connections at different points in the network.
• Locate the unserviceable section by reconnecting the
sections one at a time. In the worst possible case, it may
be necessary to remove devices one by one to identify the
faulty item.
• Cables can be checked using the ohmmeter (resistance)
function of a digital voltmeter. Isolate the power supply
and disconnect all other devices before making the check.
• For large networks, a network analyzer should be
employed. The analyzer must be suitable for use on
FOUNDATION Fieldbus networks.
Table 25. FOUNDATION Fieldbus CI852 – Fault-Finding (Continued)
Fault Possible Cause and Corrective Action