TDMS file size

[NiCoder]

We generate two files had same data values.  One is CSV format and other is TDMS file format.  The TDMS file size is alot bigger than CSV file.  Why?  

[AndreasK]

Easies answer could be values like 0 in a double channel.

0, is 2 byte

while 0 in tdms as double is 64 bit means 8 bytes which is a factor 4.

Another reason could be fragmentation of the tdms file but if you saved it with DIAdem this would not happen.

Greetings

Andreas

[NiCoder]

But why NI said TDMS file format has a small disk footprint.

[deppSu]

You can try using "TDMS Defragment" with your TDMS file which in many cases can decrease the TDMS file.

[NiCoder]

Did not help?

[Brad_Turpin]

Hi NiCoder,

I was just sent a pair of ASCII and TDMS files today which fit that description.  In that case each channel in the TDMS file had exactly 2 data values, so most of the data file was header information, not channel data.  ASCII files are more efficient at storing header information, because the structure is implied.  In the TDMS file you have binary sections for each header item, and the binary section has a code that states how big the binary section is and another code that states how many items are in the section, and another code for each item that states the number of characters in the name of the item, etc.  It adds up.  Usually the TDMS file is mostly data values, not header, and this part of the disk footprint is negligible.

Brad Turpin

DIAdem Product Support Engineer

National Instruments