system.tag.queryTagHistory - gives uncertain initial value error

Ignition
1

Hi
I am trying to access historical value of a tag (value about a minute ago)
(and subtract it from value now, to get the difference).
I am getting error ‘uncertain initial value’.
Here is my tag editor - script.

endTime = system.date.now()
startTime = system.date.addMinutes(endTime, -1)
paths = [‘[default]History/building_h/Boiler_Gas_Flow_Accum’]
dataSet = system.tag.queryTagHistory(paths = paths, startDate = startTime, endDate = endTime, returnSize = 1, aggregationMode = “LastValue”, returnFormat = “Wide”)

May be my paths is not in correct syntax, I am unable to refer to an example of the correct path…
If someone has done anything similar to this, please let me know.
Thanks in advance.

2

paths = paths seems risky. Try changing the variable name to some non-keyword.

Tip: select a block of code and press the </> button to format it. It will preserve indentation and do some syntax highlighting for you.

3

This is not an issue with python. You can safely reuse the kwarg name for the actual variable.

3 Likes
4

Try setting your tag history config sample mode to discrete and see if your results are better.

5

Did you try setting the includeBoundingValues flag to True?