Questionable Flag

In response to the polling of a point (for example, a reply from the Open Platform Communication [OPC] Server), some field devices can provide a current value and the associated data quality. When the Questionable Flag feature is enabled, protocol drivers can alert downstream krunch processes that, when said processes krunch the current value of an analog, rate, status, multistate, or rtstring point, freshness should be based on the data quality from the field.

For Remote Terminal Units (RTUs) that support device data quality, a device poll response contains both the current value and its data quality. AVEVA Enterprise SCADA software provides an option to process the value based on its data quality. Note the following:

• If a telemetered point is configured to use the device data quality and the quality is bad, the system marks the point as stale and ignores it.

• If a telemetered point is configured to use the device data quality and the quality is good, the system processes the value and marks it as fresh.

• If a telemetered point is not configured to use the device data quality, the system ignores the field device data quality and proceeds to both process the value and mark it as fresh.

For information on the Application Programming Interface (API) that supports this feature, see "Point Staling Based on Data Quality from Field Device" in the AVEVA Enterprise SCADA RealTime Developer documentation.