Data format options for logging in VeriStand

[S.Kakibe]

VeriStand can log data in Stimulus Profile, whose extention is .tdms. That include dt(time step) information, but that is not handled as waveform data in DIAdem. That way, it is a bother to gemerate time stamp data.

For example, when DIAdem opens .tdms file created by LabVIEW, the data is handled as waveform data.  So it is easy to generate time stamp data by "Numeric Channels<-> Waveform Channels" functions in DIAdem. However, .tdms file created by VeriStamd is not handled as waveform. So, it is a bother to create and add time stamp data.

Improvements: It is better to give some file format options: 1 .tdms format as waveform  2. .csv format with time-stamp

Saku

[StephenB]

Hi Saku,

Thanks for the suggestion! I had the same exact thought when using the NI VeriStand generated TDMS file in DIAdem. However, after looking into it more... it really wouldn't make sense for NI VeriStand's TDMS files to be waveform data.

Waveforms are continuous streams of data with a fixed t0 & dt. Since the data logged to TDMS files by NI VeriStand is not necessarily continuous (log triggers could go off/on/off/on)... we can't have one t0 per channel in the TDMS file unless we start creating new channels every time a trigger happens.

So the best way to view logged data from a NI VeriStand system is by using an X/Y plot. Thankfully this is really easy to do. When you create your log, make sure to also log the "System Time" channel. In DIAdem, after loading the TDMS file, use the right hand pane to select the system time channel first and then hold CTRL and select the other channels you want to plot. Then drag and drop all of those channels on to a graph. DIAdem will automatically use the first channel selected (System Time) as the X axis.

Nothing is for sure yet... but we are looking into this specifically for NI VeriStand 2012. Either with current functionality but perhaps some ease of use things... or with slightly different functionality.

[S.Kakibe]

Hello Stephen,

Thank you for your quick response and your advice. As you mentioned, logging data with system time might be one way to workaround.

As far as I heard from my customer, it is necessary to have the same time stamp of stimulus signals and model output signals at least. (This portion would be resolved to your advice.) More, he says it would be better each log file have relative time stamp referened to log start / triggered timing. I hope file log would be improved in VS 2012!

For your information, my customer wants to convert .tdms file to Vector .mdf file.(For this request, DIAdem script might work.) I feel that our customers are trying to use VeriStand with Vector tools such as CANoe. So I guess that support of .mdf file format in VeriStand logging must be one of the optionts. 

Saku

[NAKeel]

This functionality was added in NI VeriStand 2012. There is now a system channel for time that you can log and use as an X-axis in DIAdem.

[metux]

Looks like a usecase for matroska container, which does support arbitrary number of channels, hires timestamps, partial streams, indices, additional metadata, ...

(it is a very universal and standarized streaming container format).