Valid point value attributes

Valid point values for the PI point limit what values can be written to points. The following attributes are used to set valid point values:

• Zero attribute

  The lowest valid value for a point is defined in the zero attribute.

• Span attribute

  The range of valid point values is defined in the span attribute.

The span attribute value is added to the zero attribute value to specify the highest possible valid value for the point.

The zero and span attributes are required for numeric points, because the settings affect the data representation in Data Archive for these point types. Setting these attributes for other point types can affect data collection, especially if the compression and exception specifications are specified using the percentage point attributes. For digital points, Data Archive sets zero and span internally.