About Tags and the Project Database You can specify an array tag wherever you would use a variable name. Also, because array tags greatly simplify configuration tasks and can save development time, we suggest using them whenever possible. For example, suppose you want to monitor the temperature of four tanks. The conventional configuration method is: • temperature1 — high temperature on tank 1 • temperature2 — high temperature on tank 2 • temperature3 — high temperature on tank 3 • temperature4 — high temperature on tank 4 You can use array tags to simplify this task as follows (where [ n ] represents the tank number):
• temperature[ n ] — high temperature on tank [ n ] The following table contains some additional examples of an array tag: Array Tag Examples Note: When using another tag to reference the index of an array, if the value of the tag is outside the size of the array, then the following results are given: • If IndexTag is greater than the size of the array, then MyArray[ IndexTag ] will point to the end position of the array; and • If IndexTag is less than 0, then MyArray[ IndexTag ] will point to the start position of the array (i.e., MyArray[0] ). Page 56 Array Tag Example Description Tank[1], Tank[2], Tank[500] Simple arrays, where the array indexes (1, 2, and 500) are numerical constants.
For example, tank numbers. Tank[tk] A simple array, where the array index (tk) is a tag. For example, a tag representing the tank number. Tank[tk+1] A complex array, where the array index (tk+1) is an expression. For example, the value of tk (tank number) plus 1.