Dear All,
We made a set of Performance Equations to monitor the operation status concerning key equipments. Corresponding PI tags were set to be 1 for start-up while 0 for shutdown, as shown in figure 1.
The above mentioned equipment started before 1-Jan-2019, and then shut down at 5-Jan-2019 11:22:16, and then started again at around 5-Jan-2019 14:28:15, where the red arrow points to.
When I retrieved the data with DataLink PINCompDat fomula, I got the following figure 2.
There are totally 1 round of shut-down and start-up. Why do I got 10 startups and 2 shut-down there? It leads me to the suspect of compressing setting, which I attached here as figure 3.
Could you please point me to the reight direction to get only 1 start-up and 1 shutdown, according to my example here?
Thanks in advance.
Regards
ZYY
2019.01.09
To start with, in order to visualize the archive data I would turn on "markers" on the PI Procesbook Display. You will notice that your data is spaced eight hours out on average due to your compression max time. Basically, the value is not changing, but in order to show you that data is still coming in and not stale, the compression max will make sure the next value after eight hours will be archived if previous eight hours have been compressed.
Of course, I will have to recommend AF Analytics since PE service is now optional on the PI Server installation, but realities for some customers mean AF is not available.
For this type of tag I would recommend turning on "Step" since you probably don't want interpolated values if you were to sample the point. The second zero was saved due to the compression algorithm. It it rather tricky and typically not possible to obtain the desired spacing you require by adjusting compression. For what you need, it comes down to understanding the PE equation scheduling (periodic or event based) and looking at the current state and the last value written to decide if you should write a value. If the state has not changed, you could write no value using "NoOutput()" and only write values on state changes.
Let us know if you need help with the performance equation syntax to get this to work.
Regards,
Dan