TREND DISPLAY PROBLEM
the trend (10-PIC-304) show that the fuel Pressure reduced to 9 kg/cm2, the next day 11.8 kg/cm2, the day after the trend show 13 kg/cm2 and still as it is till now (at the same time when 1-C1A/C S/D). We have only the last mobile Picture of 11.8 kg/cm2 case with the existing 13 kg/cm2 (note that there is difference 1 hr in engineering station clock and operator station).
We simulate the same situation on 40-LV-602 (8 August) by opening it 100% and then 0 % closing directly the we took a trend (attached) at 8 august, the next day we took a trend and the same problem exist as mentioned above.
PLS NEED YOUR HELP TO CLEAR SUCH PROBLEM
I dont see a problem with your trend. It looks like your fuel pressure is changing.
The only thing I see is that you have zoomed in to data that does not have very good resolution in the log. So you can see the steps between the individual data points as straight lines in the trend. This is normal behaviour for the trend display.
1) Temporarily set Treatment=ExtMomentary in trend to filter exclusively on primary log's raw data points and avoid any interpolation in trend. Press L to refresh trend after any zoom (or enable Refresh on zoom in trend template to avoid presenting low res points when there exist more points in log). Point mode may give even better possibility to see value and time than line mode.
2) Extract period of high interest to CSV format from Log Configuration after selecting primary log and appropriate start time. Press Read button to read log. Actually, you can copy points from trend window after putting the ruler by clicking. CTRL-C, then paste in notepad, Excel, etc.
If historian is Basic History you can put high reliability on the values logged. They have been produced by the OPC server (and controller).