Zero

The Zero attribute indicates the lowest value possible. It does not have to be the same as the instrument's lowest value, but that is usually a logical choice. Some interfaces require that the Zero and Span match the instrument system range. See the interface documentation for details. This attribute is required for numeric data type points.

The Zero is the bottom of the range used for scaling float16 values in the archive. If the value for a float16 type point is less than the bottom of range, the value is recorded in the archive as the Under range state when the archive cache is flushed to disk. The Zero is also used when defining trends in client tools (such as PI Vision) with a vertical scale of database.

For digital points, the Data Archive server assigns the value for this attribute and ignores any edits made to it, such as with PI Builder.

This attribute is not used for non-numeric points.

A point's Zero attribute can be changed without affecting data already in the archive. For points of type float16, the old Zero is used for retrieving the archive data collected before the edit. The new Zero is used for data collected after the edit.

Note: Some interfaces use Zero information to filter incoming data. These interfaces often convert out-of-range data to digital states over range and under range. Interfaces might also use Zero configuration in other ways. Data Archive itself does not change out-of-range data except for points of type float16.