How to subscribe to OPC data changes in PowerShell

The following PowerShell code subscribes to an OPC item and displays the incoming data changes:

Add-Type -Path OpcLabs.EasyOpcClassic.dll

# Create EasyOPC-DA component 
$client = New-Object OpcLabs.EasyOpc.DataAccess.EasyDAClient

# Hook events
Register-ObjectEvent -InputObject $client -EventName ItemChanged -Action { Write-Host $EventArgs }

# Subscribe
$client.SubscribeItem("", "OPCLabs.KitServer.2", "Demo.Single", 1000)

We have tested this with QuickOPC 5.40 and PowerShell 3.0.

Note: For some issues and limitations, see How to read an OPC item value in PowerShell.

Links related to/used when writing this article:

• https://blogs.technet.microsoft.com/heyscriptingguy/2011/06/16/use-asynchronous-event-handling-in-powershell/
• http://www.get-blog.com/?p=189
• http://serverfault.com/questions/270568/need-to-add-a-wait-command-to-a-powershell-script
• http://stackoverflow.com/questions/1478545/handling-events-with-powershell