When streaming high speed data over a long period of time it is important to estimate data file size to avoid filling up your drive and also to prevent producing large, unwieldy data files. I usually try to keep file sizes less than one (1) gigabyte (FAT 32 maximum file size is 4 gigabytes) to minimize potential data losses and to make sure data transfers, analysis, and plotting don’t take too long. Whether you are using the free version of iTestSystem to manually control data file size or the paid version to automatically control file size, it is important to estimate your file size before collecting data.

iTestSystem uses the standard binary TDMS file format to stream high speed data to disk. Estimating file size depends on five (5) things.

1. Header Size (Negligible for large files)
2. Number of Channels
3. Data Type Size in Bytes
4. Sample Rate
5. Logging Duration

File Size Formula = ((Number of Channels) x (Data Type Size (bytes)) x (Sample Rate (Samples/Second)) x (Logging Duration (Seconds))) + Header Size

TDMS File Size Estimator Spreadsheet

File Size Example: Eight (8) Accelerometer Channels sampled at 2560 Samples/Second are logged as a double (8 Bytes) for 600 seconds to a TDMS data file. Estimated file size = (8 x 8 x 2560 x 600) = 98,304,000 bytes or 96,000 KB (98,304,000 bytes/1024 bytes / KB).

For more information about iTestSystem or file sizes, contact Chase Petzinger @ (844) 837-8797 x704.