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How to Scale Data from a PLC


Last Update: 11/12/2018

Kepware supports linear and squared scaling on Static Tags. In order to use either form of scaling, users must set the Hi and Low values before setting the engineering value and data type that will be visible to the client application. The Hi and Low values are sent by the PLC, and the server will perform the proper calculation on the Raw Input Value to convert it to the Engineering Value. In the example below, a device address has a value range of 0-10000. The client application needs the data as a floating point number with a range of 0.00-100.00.

  1. To start, create a Static Tag with a data type of Word.
  2. Next, select the Scaling tab and ensure that Linear Scaling is enabled.
  3. In Raw Value Range, set the Low value to 0 and the Hi value to 10000.
  4. In Scaled Value Range, set the Low scaled value to 0 and the Hi scaled value to 100.
  5. Once the tag is connected from the client application, it will be a floating point data type.

If the PLC address has a value of 27, the tag will show a value of .27; 1250 will show a value of 12.50, and so forth.

Note 1: Scaling can also be applied in reverse. If a value is written to the tag, the server will scale it to the appropriate raw value.

Note 2: If the percent deadband is being used from an OPC client, the deadband will be applied to the scaled value. For more information, refer to Scaling Data in Kepware Products.

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