How to save multi-channel multi-test data in one file

[mangoal]

We need to perform 4 channels test every 30 minutes. If we save the test data in single file it will be easier to manage it. What is the best way to do it, to be able to browse data according to test time and test channel? Thanks

[Timothy 123]

Hi,

The tdms files in labview would be a great application for recording this kind of data since you can add descriptive information like test time and test channel to your data.

Hope that helps,

-Tim

[Herbert Engels]

You can use the TDM Streaming API for fast and low-overhead writing to TDMS files. You could then use the Storage VIs to query for certain properties, e.g. test time greater than [...] or test channel = "Voltage_1". The "Read Data" Storage VI also allows for wildcards in string searches, so you could e.g. get all channels that start with "Temp".

Hope that helps,
Herbert

[DFGray]

What version of LabVIEW are you using?  TDMS is a fairly new.  If you don't have it, let us know.  There are other solutions.

[mangoal]

I am using labview 7.1, I have VIs support TDM, not TDMS. What's the difference?

[Herbert Engels]

Short version:

• TDM files have the same contents as TDMS files (file-group-channel hierarchy with properties + channel data).
  
• TDM files are not suitable for high speed streaming.
• TDM files are not suitable for larger numbers of channel (>>100 ).
• Opening and closing TDM files will get slower with new groups and channels being added.

These are architectural issues that we addressed by creating the TDMS format, which solves these and several other common issues with measurement data storage.

There is a "dirty trick" to get TDMS running with the 7.1 Storage VIs. Download and install the newest DIAdem version from www.ni.com (evaluation version). Start it up once, do nothing, close it again and uninstall it. It will upgrade the underlying infrstructure of the Storage VIs (NI-USI). USI will not be removed when uninstalling DIAdem. TDMS will not appear in the "Open Storage" dialog though. You need to use C:\Program Files\National Instruments\LabVIEW 7.1\vi.lib\platform\storage\lvStorage.llb\_openWithRoot.vi in order to open the file. See the attached example VI for details.

We are aware that many customers would like to use TDMS in versions older than 8.20 and we are looking into ways of helping you out with that. I cannot comment on a possible feature set or time frame for such a solution though.

Hope that helps,
Herbert

[DFGray]

NI-HWS is supported by LabVIEW 7.1 and will do what you want to do.  You can find it on the driver CD next to the computer based instruments.  It is also installed with most of the computer based instrument drivers (e.g. NI-SCOPE, NI-FGEN).