Precision of the Write to Measurement File Express VI

Issue Details

I am using the Write to Measurement File Express VI in LabVIEW to save data. However, when working with high-precision numeric values, the data in the output file appears truncated or rounded, resulting in a loss of precision.

Why does this occur, and is it possible to recover the original precision?

Solution

This behavior occurs because the Write to Measurement File Express VI saves data using the LabVIEW Measurement File (.lvm) format, which limits numeric values to approximately 6 significant digits.

This limitation is by design and cannot be configured within the Express VI. When data is written to the file, values exceeding this precision are truncated or rounded, and the additional precision is not retained.

Because of this, any precision beyond the supported number of digits cannot be recovered after the data is saved.

For applications that require higher numeric precision, use LabVIEW File I/O primitives instead of the Express VI. 

Additional Information

This standard was decided upon for multiple reasons. Some of the reasons include:

• The limited digits of precision reduces disk space usage for large data files.
• The prefixed length of data reduces complexity and eliminates the Express User from having to worry about formatting.
• It is actually a text file and is designed to be easily parsed and read when imported into a spreadsheet program (i.e., Microsoft Excel) or a text editor (i.e., Notepad).

LabVIEW includes example VIs that demonstrate file I/O using primitives. These can be accessed from: 
LabVIEW>>Help>>Find Examples>>Fundamentals>>File input and Output>>Spreadsheet>>Tab-Delimited Data.lvproj