Applies To:
  • CitectSCADA 6.xx
  • CitectHMI 6.xx
Summary:
I have trends configured in Citect which can take positive or negative values. When in runtime and I view these trends they trend correctly when the data takes a positive value but it doesn't appear to trend when the data is negative.
 

Solution:
There are several ways to fix this issue:

1) Check the engineering scale of the associated variable tag, it should trend all numbers within the range set. To trend negative numbers double check that the negative numbers to be trended lie within the range of this scale.

2) Alternatively, ensure that your trend tags are configured using Floating Point (8-byte samples) storage method. In addition add the following citect.ini parameter:

[Trend]RangeCheck = <Value>

where <Value> = 2 or 3 depending on whether you are also have trend data using Scaled (2-byte samples) storage method. Refer to the CitectSCADA help files for a detailed description of the citect.ini parameter above.
Keywords:
trending, negative, citect.ini, RangeCheck, engineering scale  

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