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How Do Minimum and Maximum Tags Work?


Last Update: 11/12/2018

Minimum and Maximum Tags calculate the minimum and maximum value of a Source Tag. The calculation is controlled using a separate Run or Trigger Tag (which is usually Boolean) and begins when its value transitions from a zero (Off) to a non-zero (On) state. When it transitions back to zero, the calculation stops and the Minimum and Maximum Tags retain the last calculated value. When the Run Tag returns to a non-zero state, the calculations start new.

Run TagSource TagMin TagMax Tag
01UNKUNK
1333
1838
125325
111325
075325
019325
012325
1141414
17714

The Maximum Tag can also be used in a less traditional way. For example, a customer needed to capture the state of a Boolean Tag that changed from off to on back to off very quickly. Without great frequency, it would be difficult to verify that the changes in value occurred. The Maximum Tag was used to latch this process. The source Boolean Tag was selected and a second local memory tag was used as the Run Tag, which was set to True/On. When the Source Tag changed value to True/On and back to False/Off, the Maximum Tag's value changed to 1 and stayed there. The operator then acknowledged the change and set the Run Tag False/Off and then back to True/On. The Maximum Tag value now goes to 0 if the new maximum value of the Source Tag is 0.

Note: If the server starts and the Run Tag is a non-zero value, the Minimum and Maximum value will not be calculated because the Run Tag never made a transition from zero to non-zero. If the Run Tag has never transitioned to a non-zero value, the Maximum or Minimum Tag's value will be unknown.

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