Display Point Data on a Trend Only When Another Point is a Specified Value

[SurprisedEwe1]

Is it possible to display a trend line for a historically recorded data point when another point is a particular value (such as a digital)?

In incredibly simple SQL terms this would be showing the returned data for:

SELECT AnalogueTagValue
FROM HISTORIAN
WHERE DigitalTagValue = 1

The scenario for this is that for a flowmeter that has an analogue flow value it has a digital value indicating the direction. Operations want to only see on a trend the flow when it is in or out only - i.e. the digital direction value is high, so the analogue value displayed corresponds to inflow and they would like that displayed on a particular trend. If the direction is low (outflow) then we show the trend value as 0. Vice versa, a trend could display the outflow when the digital is low.

I understand this could be done a multitude of ways by collecting the data in another point (such as using logic in the RTU or scripting to an internal point etc.), however for brevity and reducing the data stored in the historian the equivalent of a view would be nice if possible since the data is already captured, this is purely a visualisation task on the raw data. The task of making the modification would also be simpler if a SCADA solution is possible.

I was hoping that using some form of Historic Algorithm or View in the server may have allowed this and I have considered using the "Put Aside" method on the historical data by performing an override on the data when the digital is a particular value (such as overriding to 0 then having the put aside values as one of the directions), however this seems more effort than it's worth and only provides a single direction when we would like both.

[sbeadle · Accepted solution]

I can't think of another way to do this - the simplest seems to be to create a separate analog point.

[SurprisedEwe1 · Accepted solution]

Thanks Steve. I think that the best solution in our context is using Calculated Points.

One calculated point will be used for "In Flow" where it is the analogue value multiplied by the digital value, the other is for "Out Flow" which is then the analogue value multiplied by the inverse of the digital value. Then each calculated point can be used by operations as a trend line. These points will then be set as Historical but only captured by Geo SCADA and not the Client's other historian platform (this continues to only capture and store the analogue flow and the digital direction).

[MarkPitout]

Hi @SurprisedEwe1,

I see you arrived at the same conclusion I had in my head. But, for the fun of it, I made a simulation for your situation (attached).

For interest, the calculations I configured in the calculated points are:

Inflow:

IIF( ".Direction.CurrentValue", ".Flow.CurrentValue", 0 )

Outflow:

IIF(NOT ".Direction.CurrentValue", ".Flow.CurrentValue", 0 )

Be sure to set the significant change config of the calculated points to "None", or you might end up with small residual values retained in the points (eg. Outflow value is 50.0, but Inflow value is also 0.045, when it should be 0.0). 

Below a screenshot from my simulation: