Accuracy (number of decimal places) in the data received from the Web API

Hello AndreiK​ ,

Looking at those numbers and without knowing what these values represent, I feel the numbers with the more decimal places just confusing. With other words, I personally would prefer the 6 decimal places over the 16, also because there appear significant enough differences with the 6 decimal places. If those values are measurements, I also doubt if the display accuracy is a lot higher than the measurement accuracy.

As far as PI Web API's display accuracy is concerned, please refer to How to change the decimal precision of data returned in PI Web API queries (PI Web API)

I also ran a brief test and for sure I used a PI Point which is Float64.

If your PI Points are defined as Float32, then the old script is NOT giving you more accurate data. If they are Float32, the new script is giving you the correct values. What you are observing is the automatic upscaling of a Float32 to a Float64, which introduces those extra digits according to IEEE 754.

The deciding factor should not be how the PIPoints are stored but rather WHAT is the precision of the source input? If the source is a Single or Float32, and you store as a Float64 in PI, then you have introduced noise and insignificant digits to the input value. In this case, it is a false assumption to believe that the 16 digit number is more accurate.

Thanks, your answers helped to find the problem. It looks like the old script was converting tag values that were stored as Float32 to Float64