Because off-line tools by their nature are unable to report back to the appropriate person when something happens the majority of FF Power Supply manufacturers either already offer or I am confident are working on developing on-line network diagnostic modules to continually monitor and report to a central system as soon as something happens so appropriate action can be taken.
All but one manufacturer uses the Fieldbus communications protocol itself to report the diagnostic information back to the control system though each manufacturer has a different approach to making that connection and on the information they present. All but one manufacturer use a separate diagnostics module on a backplane to monitor the communications on the network.
Unfortunately, because Fieldbus Barriers, or as the Foundation calls them Active Device Couplers, have isolating circuitry between the trunk and spurs the diagnostic module mounted on the trunk in the interface room can only view information to that isolating circuitry. With Passive Device Couplers the diagnostic module typically measures signal voltage levels associated with each device.
Below is a brief synopsis of each of the present offerings on the market:
Pepperl+Fuchs released the first on-line diagnostic module http://www.am.pepperl-fuchs.com/global/en/classid_1562.htm. This design is similar to the traditional ‘signal stripper’ concept and uses serial network to transmit information to a dedicated server. The module is unique in that it can be used as either a diagnostic module or oscilloscope with the nice thing about the scope is that you can trigger it on either detection of a problem or a specific node address.
MTL were the first company to develop a diagnostic module http://www.mtl-inst.com/product/f809f_fieldbus_diagnostics_module/ using Fieldbus communications to transmit information to the control system. The MTL product is based on the Relcom FBT-6 and reports very similar statistics.
Turck uses the bandwidth capabilities of HSE with their product http://pdb.turck.de/catalogue/catalogue.do;jsessionid=541114995FC67C5AB4031E68193230B2?ID=1328152593778&OID=0000000a0001130f00030023&favOid=0000000a0001130f00030023&CMD=SELECT&act=showProductGroups&lang=en&catId=DE to provide not only basic network analysis but also information on some packet traffic as well.
R.Shahl http://www.r-stahl.com/products-and-systems/fieldbus-isbus/fieldbus-diagnostics.html manufacture the only Power Supply with diagnostics integrated into the unit itself. Diagnostics for multiple units on a common backplane are multiplexed over the H1 connection and hence control system.
There is still discussion among people installing on-line diagnostic modules about whether the Fieldbus network used to collect the data for transmission to the Control system needs to be on a dedicated diagnostic segment or whether the diagnostic module can simply appear as another device on the network with other field devices. Because these devices communicate in the acyclic portion of the macrocycle they will not change the control configuration on the network meaning it should not be necessary to upload/download anything new to the network either – just plug it in an go. Pretty nice for peace of mind when you have a potential network problem to troubleshoot.
