PCo - Listening Problems

[Former Member]

Hi,

I am observing some issues with the listening capabilities of PCo. It does seem to be ignoring the changes in the tag values once in a while. Can somebody comment on the possible causes?

Anyone else noticed the same?

I am using PCo 2.0 & MII 12.1.4 Build(53).

Regards,

Chanti.

[former_member196557 · Accepted solution]

The Update Rate is specified per OPC Source Agent, and should be a setting in the Settings tab for the agent. I believe the default in PCo is 1 second.

The notifications delivered to the Agent Instance will be at this rate even if the OPC tag that is generating the events is changing faster than that.

The Poll rate for the KepWare OPC Server Device is defined at the Static Tag definition if those are used. Otherwise, the scan rate is determined by the Update rate of the clients that are either polling or have subscribed to the OPC Server at the Update Rate.

- Steve

[Former Member · Accepted solution]

The scan rate on the OPC is 100 ms. What should be the ideal update rate on PCo? I am still having issues as far as the listening goes.

[former_member196557 · Accepted solution]

In order to catch every change that occurs at a 100mSec OPC scan rate, you should set the PCo Agent Update Rate to 50mSec. However, this will not guarantee that you will see every change in PCo. If PCo is executing the Notification event associated with a change and the Notification takes > 50 mSec to execute you will still potentially miss a value change.

Also, if your OPC Server is querying the device (PLC) for a large amount of data, it may physically not be able to read all the data in the scan rate time frame.

What are you trying to do with the OPC Server and PCo that needs this rapid an Update rate?

- Steve

[former_member192939]

Yes I Do ... For one of the OPC server .. PCo doesnt recognize the change.

For Matrikon OPC Simulator .. It does but not consistent

Please let me know if you find any solution Chanti... I will post my solution.

Regards,

Ajay.

[former_member196557]

1. What is the update rate for the OPC Agent in PCo?

2. What is the scan rate for the OPC Server connection to the device(s)?

3. Are you getting retries logged in the Agent instance log?

The update rate for the OPC Agent should be no faster than the 2x the defined scan rate for the OPC Server device connection. (i.e. if OPC Server scan rate is 1sec, PCo update rate should be no more than 0.5 sec). If the data at the device changes faster than either the OPC update, or the PCo update, those changes will not be detected:

For example, OPC Server scan rate is 1/sec, boolean tag changes from 1 to 0 to 1 within that 1 sec scan, the changes will not be detected because the value at each scan is the same. Same thing applies to any tag that can "jitter", if the jitter values are the same at consecutive scans, no change is detected.

- Steve

[Former Member]

Thanks Steve. Is the 'Update Rate' for the source system or for each Agent Instance? Can you tell me where to look for it in an Agent Instance?