AI810 value latency
One of our customers has replaced an old controller by an AC800M with CI854 Profibus Master.
He kept his 3 drops of FlexIOs and he has connected them to CI854. It works well.
But, he has also added a new S800 IO drop to his profibus network. He has observed that analog values are updated every 5 seconds on his new AI810 connected to CI801 (and profibus network). If he connects the same signal to his old FlexIOs, there is no latency and values are updated quickly.
So, we know the 4-20 mA signal is good. We know the profibus network works well for FlexIO. There is no error on CI801. Why is there a latency on value update for AI810?
He configured the CI854 to work at 500 kbits/s and all parameters follow ABB rules (provided in help files).
We have never seen this kind of problem with AI810(combined to CI801). It usually works very well.
Have you ever seen this kind of problem?
It´s hard to say where the problem lies without knowing exactly what your ProfiBus Network and I/O configuration looks like. I´ve seen a lot of problems with delays in ProfiBus installations. The main reason is normally that you try to transfer large amounts of data over a too long distance. Provided that all settings on I/O and other equipment are OK, and that there´s nothing obviously wrong with the installation, I would recommend you to calculate the delay on the bus. Normally the teoretichal values gives you an indication of what´s wrong. If calculations show delays in the area of seconds, you have to look at rebuilding the network. 500 kbits/s sounds low to me, and indicates that you may have a to far stretched network.