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Citect Trend Interpolation methods

Hemant

Hello all,

Observation is about Citect 2018. We have created Trend Tags with Sample Period of 2 Sec as below..

Trends are working fine. The observation we had now we export the trend sample in Runtime we found Sample as not for Every 2 secs what we have configured..

I check the help and found this is may be due to Trend Interpolations.

Please help me to understand 

1. Trend interpolations

2. How it affecting the Sample periods to be taken every 6 seconds and overriding the defined sample period of 2 Second.

Apreciate your help.....

Warm regards

Hemant

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  • 0

    How are you exporting the trend samples? If you export from Process Analyst, you get whatever is displayed on screen, with the number of samples/sample rate that PA chooses, and by default, only 300 samples.

    If you use the TrnExportCSV() Cicode function, you can set the sample rate (Period argument) to 2sec to get the exact samples recorded in the trends. If you choose to export every 6 seconds it will have to condense 3 recorded samples into one exported sample. The iDisplayMode arguments allows you to choose the interpolation method for each trend tag. By default, if it has to condense multiple recorded samples into one exported sample, it uses the mean value of those (3) samples. You could use Condense Mode 12 to get just the newest sample, if that's what you want. See the TrnExportCSV() help:

  • 0 in reply to Eric Black

    thank you for your reply.

    We are using CSV_Include project and its poptrend template in XGA resolutions. nevertheless yours and MARCO's explanation clearly help to understand the visualization behavoir of the trends.

    Im my case sampling period of the trend configured is 2 Sec. The trend we were using has defined 601 Samples per 1 pixels, which allows is to set a maximum duration of 20 minutes to view sample taken at 2 seconds.

    Just another query if lower the time span for 15 minutes..Still trend retrives 601 Sample from trend file and displaying.

    In this samples it showing values at 1 sec intervals as well, ideally for my trend configuration if my sample period is 2sec then values of this 1 sec intervals showb are interpolated values or calculated or what??

    regards

  • 0 in reply to Hemant

    The template you're using is very old (2002?) and uses the legacy trend object (not Process Analyst). I don't believe it supports the newer Request Mode feature. It probably just uses the default request mode.

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