topic read waveform attribute NI_DeviceNumber in DIAdem

read waveform attribute NI_DeviceNumber

faustina — Mon, 25 Mar 2013 20:54:38 GMT

I collect waveform data in LabVIEW and write it to a TDMS file. However, my users have given the same channel name to multiple channels. For example, one channel is from a high speed card and other from a SCXI card. DIAdem only recognizes one channel. How can I determine which device it came from? I know in LabVIEW there is a waveform attribute NI_DeviceNumber automatically set by DAQ. How can I access it in DIAdem? All the channels were programmatically created using DAQmx in LabVIEW.

Re: read waveform attribute NI_DeviceNumber

freighTrain — Tue, 26 Mar 2013 15:47:20 GMT

Hi faustina,

Are these channels in the same group? Are these channels written into the TDMS file together or separately?

Re: read waveform attribute NI_DeviceNumber

faustina — Tue, 26 Mar 2013 18:06:08 GMT

They are part of the same group. Each channel of waveform data was written separately.

Re: read waveform attribute NI_DeviceNumber

Brad_Turpin — Tue, 26 Mar 2013 18:16:07 GMT

Hi faustina,

If you write data from 2 different sources to the same group name and channel name with the TDMS Write.vi you will mix the data from those 2 sources into 1 array of values-- there will only be one channel. What do you see when you use the TDMS File Viewer.vi?

Brad Turpin

DIAdem Product Support Engineer

National Instruments

Re: read waveform attribute NI_DeviceNumber

faustina — Tue, 26 Mar 2013 21:58:43 GMT

In TDMS File Viewer.vi I only see one channel. I've enclosed a JPEG that shows how the data is written to the TDMS file. The waveform array has a waveform element for each channel.

Re: read waveform attribute NI_DeviceNumber

Brad_Turpin — Wed, 27 Mar 2013 16:09:50 GMT

Hi faustina,

The picture of the VI snippet you posted doesn't show whether the GroupName and ChannelNames inputs are changing each time the TDMS Write.vi is called. But if you see only 1 data channel in the TDMS Viewer.vi, then that means that you've merged all your acquired data values into 1 data channel in the TDMS file. There's nothing DIAdem can do about that, you'll want to change the acquisition VI to submit unique Group/Channel information for each separate TDMS channel that you want to create-- at the moment that you write each data buffer to the TDMS file.

We may be able to fish out values from your existing TDMS file(s) if that's important.

Brad Turpin

DIAdem Product Support Engineer

National Instruments