Solution
DAQmx Configure Logging (VI) is built for
high-speed streaming to disk , therefore it has built in optimization algorithms for data logging. It compress data while forming a file. In conventional TDMS converting VIs, this compression is not performed.
This is why converting in to TDMS and/or merging files into one will have greater volume.
If data volume is critical for your application use DAQmx Configure Logging (VI) to reduce file size.