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2PROFIBUS UK
Agenda
Typical faults
Detecting problems before they happen!
Tools for Monitoring
Preparations for fault-finding
Tools for Diagnostics
Expected PROFIBUS network quality / performance
Physical Diagnostics
Cable Tests
Stand Alone Tests
Connected Tests
Station start-up
Preventive maintenance
What to do when you have a problem
Use test Master in place of operational PLC
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Typical faults which may occur
Bus error due to erroneous wiring (physics).
Missing or additional terminating resistors
defective cables (cable carrier/cable track)
cables too long
defective plugs
Bus error due to erroneous Protocols (logic).
Parameterisation and Config
errors
Timing errors
Reflections at:line end impeadance transition
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PROFIBUS cable installation problems4
PROFIBUS Commissioning and Maintenance : Richard Needham - February 2016
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Preparations for fault-finding
Needless to say, one also needs to know how to use any available tools effectively and have reasonable appreciation of PROFIBUS wiring and protocol basics!
Accurate network ‘as built’ drawings will be useful – these might also usefully include geographic information about locations of each device within the site, where appropriate(particularly in multi-level buildings or distributed networks)
Test Points!
And hopefully a historical bench mark report against which you can compare currently measured performance
PROFIBUS Commissioning and Maintenance : Richard Needham - February 2016
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Why are drawings important?
?Testers only know the station address unless you tell them more!
Station addressing is not standard
Networks are almost never linear
The network “design” rarely reflects what was actually installed.
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Logical and physical measurements
FOC
Repeater
PROFIBUS monitoring tool
1
2
Cabinet 3
Cabinet 3 Cabinet 3
PROFIBUS DP:
Coupler
MasterSlave Slave Slave
OLM
OLM
Slave Slave
PA----DP
DP----DP
PROFIBUS Diagnostic tool
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9-pin PROFIBUS DP network plug
Optional femalePG rear testconnector
Plug for networkcableconnection toSlave or Master
PROFIBUS Commissioning and Maintenance : Richard Needham - February 2016
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Permanent Monitoring
Always online and onsite 24/7
Records issues
Notify you that something is wrong before production stops
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Network Status10
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PROFIBUS Failure:
Detection of Intermittent Device Failure
Station fails intermittently and reports back very quickly (not likely to be power)
Likely no reflection or EMC, since only one participant affected
Cause likely to be a loose connection (restarting the Station would require more time) or
internal device failure.
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PROFIBUS Failure
Missing termination at segment end
Failure caused by electrical problems on the bus
Probably no EMC because there is just one device with a significant number of repeats and
breakdowns
Recommendation: check electrical condition of the network with PROFIBUS-Tester
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PROFIBUS Failure:
Reflection rate at 100%
Missing or improper terminationPlaintext Diagnostics with Diagnostics repeater
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Timeline14
Is there a Pattern to the failures?
Do the failures correspond to outside influences?
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PROFIBUS What are we looking for?
How many devices/segments?
What is the Signal Quality like?
Idle voltage ok?
Noise or ringing on Oscilloscope?
Repeated telegrams
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PROFIBUS Test Tools
Cable Testing
Signal Quality
Oscilloscope view
Protocol Inspection
External Interference
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Cable Testers
Cable Length
Conductor Continuity
Correct Termination
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Signal Quality
The signal quality screen can give us a good idea about the cause of a problem
Test at bus end Test at bus center Test at bus beginning3 Tests The closer the test location to the error location is, the worse the overall impression (average) will be. Termination resistor is missing at station 2
A B
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Oscilloscope Views
Idle Voltage
SNR
Rise and Fall times
View by Station
PROFIBUS Commissioning and Maintenance : Richard Needham -February 2016
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Protocol Inspection
Actual messages from the Network
FDL, DP, DP-V1, DP-V2, PA and I&M telegrams
Ability to filter message recording and display
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External Interferance
Profibus
Cable
Connector
Pos 1Pos 1
Pos 1
Detects shield currents on the PROFIBUS cable resulting from
missing or wrong grounding /equipotential bonding
Follow the recommendations of the PNO installation guidelines
or Talk to Peter Thomas
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What do we want to see?
Using the Bus Status mode we can see
Baudrate
Idle voltage*
Number and Type of devices connected (Master/Slave)
Device Address’
Whether the Electrical Signal is good or bad
Whether the Packets are being transferred properly
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Looking at the Protocol
Functionality: frame analysis
Clear presentation of
PROFIBUS stations
Quick error analysis with
clear color marking and
event counter.
Plain text diagnostic messages and GSD
support
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PROFIBUS Successful network startup
Slave startsMaster is waiting for Slave
Parametererisation and Configuration
Cyclical data exchange
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Why do we need Static Diagnostic tools PROFIBUS Slave with diagnosis
Normal data exchange
Slave reports a diagnostic
Master queries the current slave status
Normal data exchange
The diagnostics information is only available in this single frame on the bus!
Master and Slave remember this status.
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Preventative Maintenance
Regular periodic testing of networks is the best way to detect problems before they become a problem
Ideal for spotting a downward trend in quality, network average
2 years ago 4600
a year ago 4000
6 months ago 3500
Todays average 3000
A good chance that in 6 months the network will not be running
Ideal for keeping your hand in with the tools so when a breakdown does occur..
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What to do when you have a problem
Don’t panic
Did anything change? (new equipment, changes to network, digger outside etc etc)
Check the Monitoring tools
Check the signal quality with PBT5
Check for errors and diagnostic messages
Make changes/repairs and re-test
Make further changes as required
Grab a coffee and relax
If you can’t work out the problem there are a number of experienced engineers in this room who offer consulting and support when you have a problem
