1761-NET-AIC to PC RSLinx problem

I'm having a problem with an Allen-Bradley network I'm working on. I was called in to troubleshoot a data collection system that was done by another technician (moved to France). They have 4 ML1200's and 4 PV300's connected together using 1761-NET-AIC cards. The PC is running RSView Works to collect data, send data and show the status of the machines. The PC is connected to the 1st AIC card on port 1 (9 pin) with a 1747-CP3 cable. The cable has been extended to about 250+ feet. I've read a few of the posts and most agree that 50' is recommended and 100' is max without repeaters. The funny part is RSView is updating the data and the network appears to be functioning normally except when I open the RSWho window in RSLinx. The customer has complained about a slow refresh rate since the beginning. I think the problem is always there but not noticed with RSView. The nodes just start dropping in and out and sometimes RSLinx just stops all together. What can I do to fix the problem? I was thinking of adding another AIC card at the PC.... suggestions would be appreciated.

Hello

Had the same type or problem using Wonderware pulling data using NetAIC units. In wonderware we found that we were pulling the date to often, i.e. every second or less. If this is the case with your RSVIEW you may need to decrease the pulling rate. I am guessing that RSView is attempting to pull data and RSLinks is also trying to attach. Also the connection to the NetNIC is I assume DH485 or Plus ? But the connection to the ML is Serial and much slower in responding to requests.

My work around is the, decrease data pulling rates and make the infromation you are gathering resident in the PLC, that is, don't make the RSView application do all the counting, etc... Add counter, timers, N7, F8 files to store date you will need in the PLC and go get it will RSVIEW every 5 minutes or so.

Good luck

Are you saying that there is an extension on the 1747-CP3 cable that's 250 feet long ? I'm absolutely amazed that it's working at all. RS232 signals, as you pointed out, are good for maybe 50 feet with normal cable, 100 feet with really good cable. 250 feet is right out.

RS-485 signals (the trunk cable running between the six-pin ports of the 1761-NET-AIC modules) can go up to 4000 feet. The way to fix this is to put another 1761-NET-AIC module close to the computer and extend the trunk cable, using the same cable type as is used in the rest of thr trunk.

Thanks for your input guys. I'll try both ideas. RSView is polling the PLC's every second which is too often for the application. Also the person who programmed the RSView put everything on one page. He has everything asking for an update at the same time. Yes, the cable is 250' long! I can't understand why it works either. I think I'll put another AIC next to the PC. Probably the easiest solution. Turns out this project was done by a student on work study. I think he was just over his head and didn't realize that there were certain guidelines you need to follow to have a stable and reliable system. Pretty ambitious project for his first attempt though!

Thanks again..