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Learn the basics of Tags in Ignition, including their purpose and use.
Video recorded using: Ignition 8.1
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[00:00] In this lesson we'll talk about Tags in Ignition. A tag is an object that contains value, timestamp and quality attributes. The value of a tag can come from different sources. A tag source will define its type. Tags can be OPC type, memory type, query type, expression type, among a few others. Generally speaking a tag's value can come from a PLC or a similar device somewhere on our network. A tag's value can also come from a database via a SQL query. Finally, a tags value can also be coming from an address in memory. This allows users to have tags be independent from a database or PLC. The source of the value of a tag determines what kind of a tag it is. And we will cover the different types of tags in a later lesson. For now what we need to understand is that tags are the main mechanism to move values or data around your Ignition projects. The main reason behind this is that all of the various resources inside of a project. Vision Windows, scripts, Perspective Views etc all have access to the tag's system. Here on my screen is the Ignition Designer. The Ignition Designer is where all Ignition projects are developed. On the left here. You will see the Tag Browser. The Tag Browser is where you create tags as well as modify pre-existing ones. Clicking on this plus sign here brings up menu with a few options. We will address the data type instance and new standard tag options in the later lesson. For now i want to focus on the browse devices option. If i click it the tag creator window will appear. Here I'll be able to browse all the OPC devices hosted by our Ignition OPC-UA server. If your Ignition gateway is connected to a third party OPC-UA server or an Ignition OPC-UA server in a remote location. You will be able to browse the tags available in those servers here. The idea is that you can always open the tag creator and then drag some tags into your Tag Browser from an OPC server. Alternatively you can select that location in your Tag Browser. Right click on it drill down to new tag. Then standard tag to be able to manually create a tag. We will cover the various types of tags what each of them do and how to create them later on. Now we can see in my Tag Browser. I have tags created already. Drilling into the OPC tags folder. I will see tags coming from one of the PLCs configured in my Ignition gateway. I'm able to see their value and their data type. If I only wanted to see the tag's value and not it's data type. I can head to the kebab dropdown here column selection. And I'm able to select what columns I want to see on my Tag Browser. As you can see my tags are currently changing in value. They're executing. What I mean by this is that tags will execute and fetch a value from their source at a rate specified by their configured tag group. Clicking on the kebab menu and selecting the edit tag groups option. Will bring up the tag group editor window. Here I'm able to see our two default tag groups. Default. And default historical. Selecting the default tag group. I'm able to see that this tag group will require a tag to execute every 1000 milliseconds. If I exit out of the tag group editor and double click on one of my sine OPC tags here. I will be greeted by the tag editor window. Notice the tag group setting and how it is linked to my default tag group. This means this tag will execute or fetch a value from its OPC source. Every 1000 milliseconds as dictated by my default tag group. From the tag editor window I can also make configuration changes to this tag. So for example, I can change the value source of the tag which changes the tag to one of the different tag types we talked about earlier. I can also configure what tag group my tag belongs to. What OPC address it's value should come from etc. I can also alter the tags numeric properties and add things like tool tip or documentation for this tag. Scrolling down a little further we're able to configure tag security in the event i only want to allow a specific role to be able to read or write to this tag. We also see options for adding tag events scripts. This is useful in the event i want to execute a piece of python code when this tag's value changes. I can also configure alarms and enabled tags history to begin logging in this tag's data. To a database of my choice. Now, if we close our tag editor here and go back to our Tag Browser. As an important concept, you're going to want to understand that tags actually live outside of your project. Currently this project we're looking at here is called tags. If I were to create a brand new project by going to file. New. New project. I won't worry about saving as I didn't make any changes. We will give this brand new project a name and title and move forward with it's creation. This project has no vision windows, perspective views scripts, or literally anything associated with it. I just created it from scratch. Yet i can see on my Tag Browser. All the tags we saw earlier from our tags project. So tags live outside of your projects. If you delete a project it does not delete your tags. This is because tags reside in the gateway. So if I were to close all my designers, vision clients, perspective sessions and all of our visualization tools. As long as the gateway is still running your tags will still be executing. So for example, you can enable tag history on a tag or configure alarms on a tag. As long as the gateway is running. The tag data will get historized and alarms configured for tags will still work.