Table 114 provides additional ADI-specific guidelines for interpretation of the Uncertain operation level result code defined in [OPC 10000-8].
Table 114 - Uncertain operation level result codes
|Uncertain_ NoCommunicationLastUsable||Communication to the data source has failed. The Variable value is the last value that had a good quality and it is uncertain whether this value is still current.
The Server timestamp in this case is the last time that the communication status was checked. The time at which the value was last verified to be true is no longer available.
In ADI, this implies that the communication to the analyser has failed, but the Analyser Server is still active and communicating with its Clients. The Clients need updates, so the Server is responsible for maintaining the namespace and all the values.
|Uncertain_ LastUsableValue||Whatever was updating this value has stopped doing so. This happens when an input Variable is configured to receive its value from another Variable and this configuration is cleared after one or more values have been received.
This status/substatus is not used to indicate that a value is stale. Stale data can be detected by the Client looking at the timestamps.
In ADI, this differs from the Uncertain_NoCommunicationLastUsable code only in that is does not explicitly state that there is no communication. For some undetermined reason, the analyser can no longer update the values. In the case of spectrographic analysers, there may be a significant error in the model that stops the collection and analysis (too many bad scans, divide by zero exception in the math model, etc.).
|Uncertain_SubstituteValue||The value is an operational value that was manually overwritten.
This value is a placeholder value that is set by the user when the instrument cannot collect or update the data.
|Uncertain_InitialValue||The value is an initial value for a Variable that normally receives its value from another Variable. This status/substatus is set only during configuration while the Variable is not operational (while it is out-of-service).
In ADI, this bit is set for all Variables when the configuration is first loaded and started. The initial value is a preconfigured value defined when the instrument is first configured.
|Uncertain_ SensorNotAccurate||The value is at one of the sensor limits. The Limits bits define which limit has been reached. Also set if the device can determine that the sensor has reduced accuracy (e.g. degraded analyser), in which case the Limits bits indicate that the value is not limited.
In ADI, some internal diagnostic value in the analyser indicates that there is something inaccurate or untrustworthy in the data. For example, in FTIR, the interferogram peak center burst location or height may be beyond the acceptable threshold. Also, the internal temperature of the analyser may be out of specification. In both cases, spectra can be collected, but the accuracy of those spectra are in doubt.
|Uncertain_ EngineeringUnitsExceeded||The value is outside of the range of values defined for this Parameter. The Limits bits indicate which limit has been reached or exceeded.
In ADI, there are multiple contexts where this code is applicable. In the instrument, it is possible that the analyser sensor or detector is close to saturated or overexposed. The analyser hardware itself is almost incapable of measuring the physical system, and thus any results from the analyser are untrustworthy. For example, if the detector saturates at 32767 counts, any readings over 28000 counts can be deemed uncertain. These limits are vendor specific.
Another example involves the mathematical modelling that occurs in the analysers. Analysers are typically calibrated and optimized to measure data and produce results in a particular range. If the inputs or calculated output exceeds that range, the validity of the mathematical calculations and results are uncertain.
|Uncertain_SubNormal||The value is derived from multiple sources and has less than the required number of Good sources.
In the analyser, the data may be an accumulation or an averaging of many measurements. If any of those measurements is uncertain or bad, then the data is subnormal.
For example, spectra are typically a co-addition or an averaging of multiple scans of the system. It is possible that some, but not all of those scans, may be bad or unusable. A few unusable scans will not prevent the system from collecting and processing the data. However, the fact that some bad scans exist should not be ignored either. If the number of bad scans exceeds a vendor defined threshold, then the data is subnormal.