OPC UA Subscription Update Faster Than 1000 ms

Updated Nov 2, 2018

Reported In

Software

  • LabVIEW OPC UA Toolkit
  • LabVIEW

Issue Details

In LabVIEW I have set up an OPC UA server and an OPC UA client that has subscription to the nodes on the server.  I want my client to read updates faster than the default 1000ms, but my client only updates once every second, just like it is running at the default update speeds.

Solution

There are a few items that control the update rate of a node that you will want to look into to make sure none of them are acting as the bottle neck in your system:
 

Create Subscription VI

The publishing interval input defines the rate, in milliseconds, that the OPC UA server returns data change notifications to the OPC UA client. The default is 1000.
 

Add Monitored Data Nodes VI

Sampling Interval

The sampling interval input (part of the monitoring parameters input bundle) specifies the maximum rate for the OPC UA server to sample its underlying source for data changes. The default is -1, which specifies that the sampling interval is the same as the publishing interval of the subscription.

Deadband

  • The deadband type input (part of monitoring parameters >> data change filter) sets the type of deadband we are implementing (none, absolute, percent)
  • The deadband value input (part of monitoring parameters >> data change filter) specifies the value of the deadband.  By default this value is 0.  The meaning of this parameter depends on the deadband type selected.
 

Write VI

The frequency at that Write.vi is called will also affect the rate that clients will get updates.  Check for the loop rate or triggers for the write that could delay the write.
 

LabVIEW OPC UA Toolkit Update Scheme

LabVIEW OPC UA Toolkit will not trigger an update to subscribed clients if the node value on the server does not change.  This means even if the other parameters and 
VIs that control the update rate are set to a value that should allow to quick updates, there will be no event triggered if the value of a given node does not change.

WAS THIS ARTICLE HELPFUL?

Not Helpful