Speed problems with RSview

Hi guys,



I have one big problem with speed on RSView SCADA. I am working in a network with one SLC500 and 7 Micrologix 1500. They are connected with westermo Optical modems. The speed is 19200 between all of them and in RSLinxs connection is defined as DH485. SCADA has around 1000 tags. the problem is that between command on SCADA and actual action in a field there is minimum 8-10 seconds delay what is tooooooo slow.
Only one station on SCADA works fast.
How to use scan classes correctly, should I set one scan class for every station.
What are the “token hold factor” and “max node address” in channel configuration tab of every PLC, and how does it affect speed?

And in general (for those with more experience) what are the most common problems for such slow link, so I’ll check if that’s the problem in my case.

Is all you data organized into contigous addresses in one data file per PLC? Data that is spread out over multiple files requires more DH polls to get all the necessary information for a screen update.

How much data is being displayed on these screens? How is it organized? Does the data for one screen come from multiple PLCs? Same result... too many DH polls necessary to update the screen.

We generally put in a master PLC at the HMI, and the HMI only talks to the master PLC. The master PLC gets the data from the remote PLC's using contigous memory locations. You can develop report on exception techniques that will make remote sites respond faster, the technique varies depending on the PLC.

I think the problem must be with the modems. I have 22 PLC's (SLC, PLC, and CL) and over 6000 tags pulling data that is not contiguous over ethernet and controlnet/ devicenet/ DH bridges and I don't have any problems with speed.

cntrlfrk said:

I think the problem must be with the modems. I have 22 PLC's (SLC, PLC, and CL) and over 6000 tags pulling data that is not contiguous over ethernet and controlnet/ devicenet/ DH bridges and I don't have any problems with speed.

Click to expand...

Agreed that data over high speed links would not be an issue, but his are over a 19,200 baud connection.

My data is not organized in continuous files. For lots of them I'm directly reading PLC inputs and some of them are analogue values (flow, pressure, current). Usually I’m reading only one bit from a word. How to organize data, to copy 200 bits bit by bit into continuous string is not so easy and I need to think on CPU load.

The slowest screen is showing data from just one PLC, other is showing from all the rest but works faster or the same.



I can't make one PLC master because if network fails I will lose all data and be unable to control anything. This distributed is safer!



This evening I have noticed that command issued from Rslogix (from another workstation connected to network) is almost instantaneous even if SCADA is working. So it looks that there is a problem between RSLinx and Rsview, because if network is congested I wouldn’t be able to send and receive data so fast from RSLogix? Or packets issued from RSLogix have priority on the network?!?



Thanks

tgaljar said:

My data is not organized in continuous files. For lots of them I'm directly reading PLC inputs and some of them are analogue values (flow, pressure, current). Usually I’m reading only one bit from a word. How to organize data, to copy 200 bits bit by bit into continuous string is not so easy and I need to think on CPU load.

Click to expand...

Think about it from this perspective.... If you data is all in one file in contigous locations the HMI only needs one DH read to get all the data from that PLC. If you data is spread out over 50 files then the PLC will need to do 50 DH reads to gather the data at a baud rate of 19200 that may take a few seconds (longer if there are errors). If you read the Allen Bradley literature on this subject they will tell you the same thing: organize the data in a contigous string in one data file to optimize your HMI update time.