About HMI tag types

Tags you create in
FactoryTalk View
 are called HMI tags.
 When you create a tag, you assign it a tag type and a data source. Tag type specifies how the application interprets data from the programmable controller or other source, and how it is represented in the application.
You can create and use three types of HMI tags based on the data that they can store:
  • Analog tag
     stores a numeric value from a range of values defined for the tag. Use them to represent devices that can have a range of values such as temperature, pressure, flow, or the position of a rotary control.
  • Digital tag
     accepts any numeric value. Zero will be written as False (0) and any non-zero number will be written as True (1). Use them to represent devices that have two states: on or off, such as switches, contacts and relays.
  • String tag
     stores ASCII strings that can be a string of characters or whole words. The maximum size string allowed is 82 characters. Use string tags to represent devices that use text, such as a bar code scanner that uses an alphanumeric product code.
In addition to the tags you create, the application provides a set of
system tags.
TIP:
  • In discussions about setting up communications for the application, you will find the terms
    device tag
     and
    memory tag
    . These refer to the data source specified for a given tag, rather than the type of data it accepts.
  • The maximum number of alarmable tags allowed is 40,000 per HMI server, 10,000 of which can be analog tags.
  • Each graphic display can contain up to 1000 expressions or references to tags.
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