Unable to see signal that changes infrequently

[Bayden Smith]

I am trying to do analysis of various process variables against their setpoints.  I do this by trending the various variables along with setpoints.  Some have calculations to determine differences or sometimes multiple setpoints are needing to be added to get a final setpoint.  When I add the setpoint signals, some will not display unless they have changed in the viewing window due to the infrequent data points.

I can increase the maximum interpolation but this still only works if there is a change in the viewing window (but does give me the line back to the previous change).

Since each setpoint can change multiple times a day or remain constant for weeks at a time this makes this difficult to use reliably.  I can always use a fixed value but then I will need to change it when the setpoint changes and is not workable on a live trend.  I can replace invalid values with another one which works, but this is the same issue as using a fixed value in that it will not necessarily be the correct value for a live trend.

Is there anyway to get around this limitation?

[John Cox]

Hi Bayden,

I would try something like this in Seeq Formula, on the signals that change infrequently:

$signal.validValues().toStep(30d)

In place of the "30d" you would enter the maximum time that you want to connect data points and to see the lines drawn. Given you are working with setpoints, I would recommend converting them to step interpolation using .toStep(). 

If that doesn't get you to the final result that you want, you can add one further function:

$signal.validValues().toStep(30d).resample(1d)

The resample will add more frequent data values at the period you specify (change the "1d" to whatever works best for you). You do need to be careful that you aren't adding any incorrect or misleading values with this approach, based on your knowledge of the signals.

Let us know if this helps. I believe you can get a solution you are happy with.

John

 

Edited March 21, 2022 by John Cox

[Bayden Smith]

Thanks John,

That is perfect and gives me exactly what I am after.

I was already making them toStep() so I wouldn't get a join the dots line, but was unaware of the '30d' part of that formula.

Regards,

Bayden