I've just completed a design proposal based on Profibus PA. The design greatly simplifies wiring and offers big savings. However I've been told that the client has decided to stick with analogue because the maintenance techs hate fieldbus! has anyone else had this issue and can anyone tell me why maintenance techs hate it so much?

In my experience of using the Phoenix Interbus and Profibus the 'techs' prefer what they know because for them that is easier to 'fix'. If a customer asks their techs for their opinion the 'negative' one tends to win out. In my days as an automation comissioning engineer I used to find that the maintenance guys/gals were in fear of fieldbus because for them it was like 'Black Box' tecnology and of course they were not working on it for long enough periods to build up sufficient 'fault finding' experience. The system can run ok for long periods and then when it goes down they get in a pickle because they cannot remember what to do. For us commisioning guys/gals it was not an issue because we worked on it everytime we commissioned a new system and so fault finding was relatively easy. This can be more important of course when certain field bus faults effect large parts of the automated system and thus increase the pressure for a quick resolution.

Regards.

This is probably the real reason rather than one of reliability. Its been a while since I've done any fault finding so I don't know what tools are available but I would have thought that there must be some simple to use hand held analysers to make fault finding easier. It can't be much more difficult than fault finding an analogue loop can it?

The main tool is usually a laptop and relevant software......but not all techs are comfortable with this. It is not easy however to start talking about the methods for fixing something when trying to sell it, as I am sure you are aware.

Regards.

alamatec, I have spent the last decade designing, modifying, & commisioning various profibus DP/PA, devicenet and AS-i fieldbus type systems including safety based systems. I would choose 4-20mA and digital I/O over and over again. Although there are initial installation cost savings for fieldbus systems, 4-20mA is more reliable and easier to fault find on in the long run. Multi-meter vs dragging laptops out at 3am is a no brainer! You will find every maintenance electrician will say the same. Keep it simple.

Edited: 16 December 2011 at 11:21 PM by neilparsons