Question

Which formula do I use to scale an analog input if my engineering unit does not start at 0?

Answer

Click here for scaling formula.

a. When using BCD or Binary data types, you will lose resolution since you cannot use the fractional values. You can multiply the engineering min and max values by a factor of 10 or 100 to accommodate for this to a certain extent. For example, if your engineering range is 0 to 100, use 0 to 10000.
b. If you are dealing with negative values in DirectLogic PLCs, it will be easier if you use floating point data type.
c. Ladder example using IBOX to scale -10 deg C to 60 deg C, where V2000 is the raw count (0 to 4095):

Click here for scaling example using IBOXs.

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FAQ Subcategory: CPU & Programming

This item was last updated on 2009-03-23
Document ID: 1182

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