Diadem: Save as time vector as "DDC_Timestamp"

[phjordan]

Hello,

I am writing measurement data into .tdms files using LV 2009 SP1. Time is recorded in timestamp format into a seperate channel. Due to an error in group and channel naming on the LV side, I have renamed group and channel names in existing .tdms files using Diadem 11.1.

Apparently, the result was that the format of the time channel is no longer "DDC_Timestamp" but "DDC_Double".

I use Matlab for postprocessing the data, and in order for my scripts to work, the time channel needs to be in "DDC_Timestamp" format. Is it possible to modify the .tdms file in Diadem in order to re-convert the time channel format from "DDC_Double" into "DDC_Timestamp".

Any help is appreciated, best regards

Philip

[RamonaL]

HI Philip,

what you can try is, changing the property " Anzeigeformat" or "displaytype" of the channel. The thing is, that even timechannels are stored as float 64 bit format on the disc. So the only difference is the way DD interprets the data. Try that!

cheers, RMathews

[phjordan]

Hi RMathews,

thank you for your reply. Unfortunately this did not seem to work for me. When reading the tdms file into Matlab, the function DDC_GetDataType still returns "DDC_Double" for the time channel.

I also tried the ChnPropSet("Timegroupname/timechannelname","datatype","DT_Date") function from within the Diadem Script panel, but this returns an error. I am not familiar with using the Diadem functions.

Philip

[RamonaL]

Do you save the channel in LabVIEW as a timechannel? Or as a numeric channel? Maybe we can change here something.

[Brad_Turpin]

Hi RMatthews,

LabVIEW has the option to save the time channel data as either a double (orange) channel or a set of 8 U16 integers (brown).  DIAdem only has the option to store time channel data as a double.

You could rename the channels/groups in LabVIEW instead of DIAdem and preserve the (brown) datatype of the time channel that way.

Brad Turpin

DIAdem Product Support Engineer

National Instruments

[Brad_Turpin]

Hi RMatthews,

I asked R&D about this and got updated information.  DIAdem 11.1 and previous versions behaved as I described above, namely they always saved DBL time channels in TDMS 1.0 files.  DIAdem 2010 and later versions always save the same integer cluster time channels that LabVIEW does, using TDMS 2.0.

Brad Turpin

DIAdem Product Support Engineer

National Instruments

[RamonaL]

Hi Brad,

thanks for that information, that will be be hopefully helpful!

Thanks a lot, Mona

[phjordan]

Hello Brad, RMathews,

a little bit late, but thank you very much for your numerous replies. Much appreciated!

cheers,

Philip