<Update Type> Status attributes such as Current Status and Previous Update Status are common to points on many drivers. They indicate the status of the particular point value to which the attribute relates (as opposed to providing general information about the status of the point itself). For example, a point’s Previous Update Status attribute only indicates the status of that point’s Previous Update Value.
With points on the DNP3 driver, <Update Type> Status attributes might display a common value and/or any of these driver-specific values:
- Chatter Filter—Only applies to binary input points. The recorded point value might be inaccurate as the point was experiencing a rapid series of state changes at the time of the update. This Status value might indicate a problem with the sensor.
- Comms Lost—Only applies to physical points on remote devices, such as another DNP3 outstation that is downstream of the outstation from which Geo SCADA Expert obtains the points’ data. Communications between the outstation and remote device were lost at the time of the update. This status indicates that the point value used for the update was the value that the outstation last reported (as this was the last known point value at the time of the update).
- Discontinuity—Only applies to counter points and frozen counter points. The point value might not be a true representation of the point value at the outstation, as the counter’s change in value could not be ascertained. (The outstation was unable to compare the counter value against a previous value, to obtain the correct count difference.)
- Local Forced—The point’s value was ‘forced’ (overridden) locally at the outstation at the time of the update. The value might have been forced, for example, by a program running at the outstation, or by a local access device.
- Offline—The point value might not be a true representation of the value of the measuring instrument or control device to which the point relates. This status indicates that the database point in Geo SCADA Expert was processing its point updates correctly at the time of the update, but the value that Geo SCADA Expert received from the outstation was ‘stale’ (unchanged). The status indicates that the outstation was not updating the point in its local database at the time of the update.
- Online—This is the expected Status value for a point that is active, and on an outstation with which Geo SCADA Expert is communicating successfully.
- On its own, this Status value indicates that Geo SCADA Expert obtained the recorded point value from the active point as expected.
- If the Online Status value is accompanied by other Status values, this might indicate an inaccurate point value.
- Omission of this Status value indicates that the data should be treated as ‘stale’ (unchanged) and/or suspect.
- Overrange—Only applies to analog points. The recorded point value exceeds the point’s valid measurement range. (The point value exceeded either the Full Scale limit or Zero Scale limit, and was reported as being ‘out of range’ by the outstation (see Specify how the Driver Determines whether a Reported Value is Out of Range).)
- Many DNP3 outstations do not support downloading of configuration properties from Geo SCADA Expert, but the limits in Geo SCADA Expert should replicate the configuration that exists for the point at the outstation.
- Reference Error—Only applies to analog points. The recorded point value might be inaccurate, due to a fault detected with the point’s measurement process. For example, it might be that the sensor needed recalibrating at the time that the data was reported, or the raw data was affected by a significant amount of interference.
- Remote Forced—Only applies to physical points on remote devices, such as another DNP3 outstation that is downstream of the outstation from which Geo SCADA Expert obtains the points’ data. The point’s value was recorded while the remote point was ‘forced’ (overridden) locally by the device on which the point is located.
- Restarting—The DNP3 outstation on which the point is located had restarted, but had not had chance to scan its I/O at the time that Geo SCADA Expert read the data. Such data should be treated as suspect as it will typically be one of the following:
- The last known value of the point, before the outstation restarted
- A default value (such as zero)
- A random uninitialized value.
- Normally, a DNP3 outstation scans its I/O as soon as it starts up, so you would not expect to see this Status value. However, this Status value might be reported by a point that is on a remote device—a device that is downstream of the outstation from which Geo SCADA Expert obtains the point’s data.
- Rollover—This Status value has now been deprecated by DNP3, but may still be used by counter and frozen counter points on some older DNP3 devices.
- The DNP3 protocol does not have a mechanism for reporting the value at which a counter rolls over. Instead, the SCADA master (such as Geo SCADA Expert) is expected to poll a device frequently enough to detect when a rollover has occurred. This Status value indicates that the recorded point value is for such a rollover.
With each of the above Status values, the associated Quality attribute should provide more information about the reliability of the point’s data and/or the source of the point value.
For further information about <Update Type> Status attributes and other attributes that are common to many types of point, see Status Attributes Associated with Points in the Geo SCADA Expert Guide to Drivers.
With DNP3 points for which Geo SCADA Expert stores data historically, the above Status values also appear in Historic Lists (see DNP3 Specific Status Descriptions on Historic Lists).