The back story: We have an analyzer which gives a new output every 20 minutes and holds that output for 20 minutes until it processes the next sample and then changes the output to the new value. So if we look at the compressed data, what we should see is Date/Time value, Date/TIme + 20 min, value, etc.
Now what is happening is that somewhere in the system and I assume that it is in the PI data sampling section, PI is adding a pseudo point one minute before the actual point. As a user, I have been unable to locate anyone at our work who can explain why the extra data point is being added and sofar no one has the time to help me resolve this issue, so I am forced to manipulate the data and delete the extra point myself.
My theory is that with a stair stepped input, PI is adding a data point so that it is able to trend the last time period (20 min) worth of data. I'm guessing that there is a switch setting somewhere to tell PI not to do this but unfortunately have no control over the creation of the data. This bogus point is generally close to the actual value but sometimes is way off. And I know that it is somewhere in our system from the RTU to being stored in PI as I have checked the actual outputs from the analyzer to be sure it is not putting out two values.
My idea is this, using Compressed Data to retrieve the TagName's values, I want to filter the data selected to ignore a reading where the NextEvent is less than 2 minutes from the current event being processed. But doing this in PE, I need to know what the current time of the data is so I can check its time against the time of the next event.
If you are retrieving data over say a month and grabbing every reading, I need to be able to deterime the time of the current reading being processed?
Anyone got an idea on how to do this? It's no problem doing it programatically but I would like to be able to display the actual data in ProcessBook.
Below is a sample of the data and I have marked the extra readings.
01-Jul-13 00:02:35 55.6636467 FALSE
01-Jul-13 00:03:35 52.35025024
01-Jul-13 00:23:35 52.35025024 FALSE
01-Jul-13 00:24:35 52.92341995
01-Jul-13 00:42:35 52.92341995 FALSE
01-Jul-13 00:43:35 53.27281952
01-Jul-13 01:02:36 53.26889038 FALSE
01-Jul-13 01:03:35 51.5258255
01-Jul-13 01:22:35 51.5258255 FALSE
01-Jul-13 01:23:35 50.09289551
01-Jul-13 01:42:35 50.09682465 FALSE
01-Jul-13 01:43:35 49.99868011
01-Jul-13 02:02:35 49.99868011 FALSE
TFG