Create units of measure

You create units of measure for a UOM class in the UOM database.

1. In the navigator, click Unit of Measure.

2. In the Unit of Measure browser, select the class to which you want to add a new unit of measure.

3. Choose from the following actions.

   • On the toolbar, click New UOM.

   • Right-click the class in the browser and select New Unit of Measure.

   • Right-click in the UOM viewer and select New Unit of Measure.

4. In the Unit of Measure Properties window, enter a unique name for the unit of measure in the Name field.

   Note: The name cannot be the same as a previously defined UOM abbreviation or UOM name.

5. In the Abbreviation field, enter a unique abbreviation for the unit of measure.

   If UOM case-sensitivity has been enabled, you can use the same abbreviation as a previously defined UOM abbreviation, so long as the case is different. For example, you can use FR, fr, Fr, and fR for four different UOM abbreviations.

   Note: The abbreviation cannot be the same as a previously defined UOM name, regardless of case.

6. Optional. In the Description field, enter a description for the unit of measure.

7. In the Reference UOM field, select the unit of reference class from which the new unit can be converted. The default value is the same as the read-only Canonical UOM value.

8. Choose one of the following conversion methods.

   Caution: Conversions that are based on Formula have some limitations as well as impact on performance. You should only select Formula when Simple conversions are inadequate.

   Option	Description
   Simple	Converts a UOM based on scaling factor and base offset values that you enter in the following fields. In the Factor field, enter the conversion factor from the reference UOM to the new UOM. For example, °C has a factor of 1 relative to kelvin. In the Offset field, enter a conversion offset from the reference UOM value. For example, °C has an offset of 273.15 from kelvin. Note: Although PI AF supports time-weighted totalizations that can automatically assign the appropriate units of measure, it is essential that the conversion factor of the UOM be defined to as precise a level as possible for this feature to activate. For example, if you were to define a flow rate UOM such as US gallons per day with a conversion factor of 4.38126E-08, automatic conversions for this UOM would be disabled, whereas if the conversion factor were 4.381263638889E-08, automatic conversions would be active.
   Formula	Converts a UOM based on a complex conversion calculation. For more information, see Unit of measure conversion calculation.

9. Optional. To establish an alternative UOM name so that users can see attribute values returned in their preferred UOM, in the Mappings list, select a UOM name from the Mapping list for each UOM group.

   Note: Although default mappings are provided for Metric and US Customary, you can modify them as needed. To modify multiple UOM mappings in UOM groups, use PI Builder.

10. Click OK to save the new UOM.