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Advanced analog points do not change values in Geo SCADA

Published date: 09 November 2020

Problem:

Some or all of the advanced analog points in my Geo SCADA application do not update when communication is good. The advanced digital points update as expected. How to fix this issue?

Solution:

If quality of communication to the source is good and the advanced digital points update as expected, consider checking the Significant Change property of the advanced analog points. It is possible that the Significant Change property of the advanced points is either set to None or to the Percentage of Span where the Span is far larger than the expected change in each point's value. This only applies to current data for analog points.

Geo SCADA makes use of the significant change feature to filter out minute changes otherwise known as "noise". This is useful when values read from the source tend to fluctuate during normal operation such as readings of pressure, temperature, flow etc.

The Significant Change property can be set to None, Percentage of Span and Absolute. 

Significant Change = None.

If the Significant Change is set to None on an advanced analog point, the value of a point would only update in Geo SCADA when:
  • The point changes state
  • The point's Scan Group interval expires (this applies to points on outstations that are using direct, rather than PSTN, communications to talk to the server)
  • On start-up of a call to an outstation (this only applies to points on PSTN outstations)
  • The Refresh action is triggered for the outstation on which the point resides
  • On system or driver start-up
In other words, setting the Significant Change to None is often undesirable if the value of a point is expected to update automatically during a scheduled poll. Please check if Significant Change is set to None if your case.

Significant Change = Percentage of Span.

An issue might arise if the span is configured to be too large or the percentage of span itself is too large or a combination of both. For an analog point in Geo SCADA, the span is defined by the difference between the Full Scale value and the Zero Scale value for some drivers and Overrange and Underrange for others. When Percentage of Span is used, Geo SCADA would only accept values if the change in the value is greater or equal to the percentage of span in addition to the reasons listed in None. Please check whether the span is configured within the reasonable range and/or the percentage of span is adequate.

Significant Change = Absolute. 

When the significant change is Absolute, Geo SCADA would accept a change in the value only if the value changes by the defined amount in addition to the reasons listed in None. Please make sure that the Absolute deadband is set to an adequate threshold.

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