Hi everyone,
I have found that the data retrieved by the PI Datalink is not exactly the same as the archive editor. why is that? if I would like to have the same, how to do?
Is there anyone know about this? help me please.
Thanks in advance.
Hi everyone,
I have found that the data retrieved by the PI Datalink is not exactly the same as the archive editor. why is that? if I would like to have the same, how to do?
Is there anyone know about this? help me please.
Thanks in advance.
Tors
In your original post, you asked:
First, let us understand that what SMT showed you is correct, and what Excel showed you is not fully correct. It is important to understand the WHY. SMT is displaying the numbers in their stored precision as a Float32 or Single. Excel is displaying the numbers as Float64 or Double, which introduces an error due to the conversion.
Consider the Single value of 750.246. When converted to a Double, it becomes 750.2459716796875.
In no way should you assume that more digits means more accurate. The bottom line is to trace the values back to their point of origin, perhaps a controller in the field. That controller most likely uses Single, so the PI Data Archive should likewise use Float32. If you defined this tag as an AFAttribute, its data type should be Single.
The IEEE 754 Converter website may be found in these other posts:
https://pisquare.osisoft.com/s/question/0D51I00004UHkaKSAT/storing-significant-digits
Plus those other posts try to explain the oddity in better detail. All of these should help answer your first question.
Given the display difference between SMT and Excel, the answer to your second question is: you cannot make them the same since by their very nature they are different. One displays the numbers as they are stored, and the other performs a data conversion.
Tors
In your original post, you asked:
First, let us understand that what SMT showed you is correct, and what Excel showed you is not fully correct. It is important to understand the WHY. SMT is displaying the numbers in their stored precision as a Float32 or Single. Excel is displaying the numbers as Float64 or Double, which introduces an error due to the conversion.
Consider the Single value of 750.246. When converted to a Double, it becomes 750.2459716796875.
In no way should you assume that more digits means more accurate. The bottom line is to trace the values back to their point of origin, perhaps a controller in the field. That controller most likely uses Single, so the PI Data Archive should likewise use Float32. If you defined this tag as an AFAttribute, its data type should be Single.
The IEEE 754 Converter website may be found in these other posts:
https://pisquare.osisoft.com/s/question/0D51I00004UHkaKSAT/storing-significant-digits
Plus those other posts try to explain the oddity in better detail. All of these should help answer your first question.
Given the display difference between SMT and Excel, the answer to your second question is: you cannot make them the same since by their very nature they are different. One displays the numbers as they are stored, and the other performs a data conversion.
