hey folks,
we are experiencing an issue with one of our profibus PA networks where devices are randomly dropping off the network resulting in a bus fault which stops devices communicating (sometimes 2 and other times all 18).
The configurations is S7-414 CPU---> DP Link ---> DP/PA Coupler then out on the PA bus to 18 devices in total. The devices are a mixture of Flow, Level, Pressure & Conductivity transmitters which are all endress and hauser instrumentation.
Several weeks ago a contractor company came in and installed 2 new devices to the bus (one flow tx promag 50 and one cerebar pressure tx). ever since this installation we have been experiencing random faults where the PLC is unable to communicate with some devices on this bus. (nb there are 6 PA loops on this PLC and all others are running healthy).
A service guy from siemens came out last night and had proficore / profitrace analyser and confirmed that devices were randomly dropping off the network and if monitored for long enough each node had eventually faulted but not in any sequence or pattern.
Checked the PA waveform which was clean at 900mV peak to peak with no noise or spikes.
All cabling has been checked and screens belled out to ensure good connection all the way back to the final termination in the control panel.
One thing that places doubt in the whole thing is that sometimes when you go online via hardware manager and view each instrument. some devices dissapear off the PA loop and if you go offline then back on they re-appear???? surely if a device was unable to communicate it would appear with a red cross or slash above it???
Has anyone came accross this before? I am now at a stage where we have checked everything physical on that PA loop but have doubt in the config.
Many Thanks
LH
we are experiencing an issue with one of our profibus PA networks where devices are randomly dropping off the network resulting in a bus fault which stops devices communicating (sometimes 2 and other times all 18).
The configurations is S7-414 CPU---> DP Link ---> DP/PA Coupler then out on the PA bus to 18 devices in total. The devices are a mixture of Flow, Level, Pressure & Conductivity transmitters which are all endress and hauser instrumentation.
Several weeks ago a contractor company came in and installed 2 new devices to the bus (one flow tx promag 50 and one cerebar pressure tx). ever since this installation we have been experiencing random faults where the PLC is unable to communicate with some devices on this bus. (nb there are 6 PA loops on this PLC and all others are running healthy).
A service guy from siemens came out last night and had proficore / profitrace analyser and confirmed that devices were randomly dropping off the network and if monitored for long enough each node had eventually faulted but not in any sequence or pattern.
Checked the PA waveform which was clean at 900mV peak to peak with no noise or spikes.
All cabling has been checked and screens belled out to ensure good connection all the way back to the final termination in the control panel.
One thing that places doubt in the whole thing is that sometimes when you go online via hardware manager and view each instrument. some devices dissapear off the PA loop and if you go offline then back on they re-appear???? surely if a device was unable to communicate it would appear with a red cross or slash above it???
Has anyone came accross this before? I am now at a stage where we have checked everything physical on that PA loop but have doubt in the config.
Many Thanks
LH
