Is there a way PI can imput an fixed offset befor arckive the data?
If you wish to modify the data in the archives then would need a Performance Equation that changes the raw value every time it is archived. This is generally not recommended as we want to preserve the original values.
If you are using PI AF or other clients, refer to the following:
AF Unit of Measure (UOM) Conversions
UOM Automatic Conversions Using PI Analysis Service
Retrieving data ...