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Learn how to configure a Leased Tag Group, a Tag Group where Tags vary in execution rate based on whether they are currently being viewed.
Video recorded using: Ignition 8.0
Transcript(open in window)
[00:00] Ignition offers a built-in way of executing a tag at one rate when it is being viewed in a client, session, or designer and executing at a different rate when it is not. This is useful when trying to minimize use of network and PLC resources by only subscribing at a fast rate when tags are in demand. We can do this using a leased tag group. You can see I have the designer open here. And in my Tag browser, let's start by configuring a Tag group. So I'm going to click the Stopwatch icon here. And then I have my default tag group already, but I want to add a second one. So I'm going to click the Plus icon here. And let's change its name. Let's just change it to Leased Tag Group. And then let's set its Mode to Leased. So I'm going to select Leased here. And we can see that one additional property appears in the Tag Group Editor, this Leased/Drive Rate property. Now, between these two properties, the Rate and the Leased/Driven Rate, the Rate property corresponds to the rate we'd like to use when nobody is looking at this tag, meaning there are no clients, designers or sessions open that use this tag. I want to set this rate to be rather slow. Let's say five seconds for now. So I'm going to enter 5,000 milliseconds here. And then right below it, the Leased/Driven Rate is the execution rate we'd like to use on our tags when the tags are visible, meaning, for example, they're tied to some component that's open in a client or session. So that's actually all the configuration that's necessary for configuring a leased group. So I'm going to click OK here. And then now let's create a tag. So in the Tag browser, I'm going to right-click on my Tags folder. And under New Tag, I'm going to select New Standard Tag and then OPC Tag, and then I'll pull over the Tag Editor here. Let's just give this tag a name of My Tag. And then let's set its Tag Group to the Leased Tag Group we just created. And then I want to point this OPC Tag at some OPC address. So I'm going to click the icon next to OPC item path, and then I'm going to browse in Ignition OPC UA Server until I find my Generic Simulator. And let's just pick a Sine tag. Let's say Sine0. And then I'll hit Commit. And then to see this in action, I'm going to click OK. And we see that our tag has been created. Note that it's executing at a five-second rate here. Every five seconds the value changes. This corresponds to the slow rate we configured. Currently, this tag is not being used anywhere, not in any sessions or clients or in any designers. Now, let's say that I change that. So just for the sake of demonstration here, I'm going to click on my tag and drag it into this view that I have open. And then let's say we put it on an LED display. Note that immediately the tag is now updating at a one second rate. Now I've demonstrated this in the simplest way possible just by dropping my tag onto an open view in the designer. But this functionality will also work, again, from any clients or sessions that are open as long as those clients or sessions are using this tag in some way. So now if I go ahead and delete my display, and I select Yes, we see that our tag goes back to the five-second rate. So that's all it takes to configure and use a leased tag group. Leased tag groups can be an effective way of trimming down on system, network, and PLC resource usage when tag values aren't in heavy demand.