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| 4/28/2011 11:16 AM | |
Joined: 10/7/2005 Last visit: 11/18/2024 Posts: 3027 Rating:
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Hello GoForIT
It may be or may not be is the only truthful answer I can give you. PAnetwork design allows for stublines and appears in general to bedeceptively simple. There are however a fair few rulesrules involved (and not always adhered too by designers/installers) to ensure you comply with the PA standard. Possibly most importantly in your case is the permissible PA Spurline (aka Stubline) lenght which is a function of total number of PA devices and the following applies in non-EX installation: 01-12 PA devices: 120 m Spurline per device 13-14 PA devices: 90 m Spurline per device 15-18 PA devices: 60 m Spurline per device 19-24 PA devices: 30 m Spurline per device 25-32 PA devices: 0 m Spurline per device You used to have only 17 PA devices on the bus which meant every PA device could have had a Spurline lenght of up to 60 meteres. By adding three more, you now are limited to only 30 meters of Spurline per device which also applies for all thealready installeddevices (this is typically the biggest problem when adding devices to existing PA networks). Note that aspurline is defined the piece of cable from the device until the point where it meets the main"trunk" (the piece of PA cable which sits between the two terminators is the trunk).
There's plenty, see above and also the attached PA installation guideline (available for free also from http://www.profibus.com/downloads/).
Yes, but make sure that the terminator is also on at the PA coupler in your case.
Buy Procentec's ProfiTrace 2 Troubleshooting toolkit Ultra Pro (PA probe included) and analysethe bus. Last but not least, a useful tool to verify PA design (and/or FF design) is P&F Segementchecker (best of all its freeware) I hope this helps AttachmentPROFIBUS_PA_Installation_Guideline_V2.2.pdf (287 Downloads) |
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| 4/29/2011 10:20 AM | |
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Joined: 10/7/2005 Last visit: 11/18/2024 Posts: 3027 Rating:
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Hello again GoForIT
Irrespective of the number of spurlines, split connects, PA junction boxes etc, thewhole PA Segment that originates from the PA coupler is still one digital fieldbus. As such it can be brought down by in its entirety by things like outside interference or signal degradation due to poor installation,too long spurlines etc. Note too that even though (Manchester Bus powered based) PA Segmentsallow for spurlines (unlike RS485 based DP segments where they are best avoided all together), they still cause reflections and signal degradations (PA is just better at tolerating these, more so since its speed it fixed at a rather leisurely 31.25 Kbps). My guess is that the signal qualitywas already poor onyour PA network before you added three more devices to it and that the addition of them was the proverbial straw that broke the camels back (as said before, a PA capable bus analyser is the best way to find out).
Not with the Siemens DP/PA link which you do have (it actually does NOT allow you to adjust the bus paramters on the PA side and whatever parameters you have on the DP side would affect the DP network but are irrelevant for the PA side of things).
Unfortunately there isn't and I'm not too sure who to blame for this (P&F and Siemens are the only manufacturers of DP/PA links and couplers and perhaps aren't interested in supporting a "competitors" product). It doesn't matter all that much though since you can use the generic power supply (tick "integrated Master/host" and "Terminator" andnonimate its Supply Voltage and max. supply current),add generic field devices (and nominate their input current and minimum Voltage) and use simply 3 way junction boxes to represent your Split Connectors (btw, I personally prefer to use junction boxespreferably with segment protection feature or Active Field Distributors instead of split connectors). I hope this helps |
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