Quering a TDMS file

[k-waris]

I am rather impressed with ease and efficiency of TDMS logging especially with Daqmx Configure Logging.vi bypassing OS non-determinism and storing straight in defined file within Hard Drive.

I managed to store a large TDMS file logging over 250KS/s.

Initally I thought I would have to do database programming but TDMS technology seems to be working ok. There is however a limitation which probably could not be resolved and I might need to reconsider the databases.

How much data could we load on a 1000 px graph logging over 100KS/s. I designed some customized cursors and they only work when file is logged at 1KS/s for duration nearly an 1hr. At any higher sampling rate, my beloved cursors just go unresponsive!!

Secondly, the only sort of 'Quering option' that I could see with TDMS is using 'TDMS Set Next Position' vi. Like with databases, could we tell TDMS to extract say all points from 2200 to 2300 pm?

Many thanks in advance

K Waris

[crossrulz · Accepted solution]

The TDMS Read does have an Offset and Count inputs to just get the samples you want.  The hard part will be figuring out which samples you need.  It will just take a little bit of math since you know the start time and the sample rate.

[Hooovahh]

If you are writing code to generate your own graphs the offset and length are probably the tools you want.  But if you are looking to open large TDMS files in general, I suggest Scout by Signal X.  Very useful tool that handles large files with lots of graphing tools.  I believe it is still free for most features.

https://www.ni.com/en/support/downloads/tools-network/download.scout-tdms-editor.html