digital sampling

[Dennis_Knutson]

Putting your original VI in a new location doesn't make any difference. Did you not understand what I said about creating the LLB with all files and posting it here?

Try an experiment with just the analog and digital acquisition in a loop. Delete everything else except for the digital indicator and see if the acquisition timing is adequate. Add things back in one at a time to see what is causing the bottleneck.

[sdonah2]

I think that I have made some progress, but I am stuck with two problems now.

1. The Labview Measurment file properly records the analog values but not the digital values. It puts all the digital values into one col. with a incorrect value.

2. The LVM only records 100 data points then stops.

Thanks for your help

[Travis_M.]

Good evening Scott,

Forgive me for coming into this conversation a little late.  I was unable to run your VI because you did not include the Sub-VI in the attachment (see previous posts on how to do this), but I did take look at your VI -- it looks like the reason you are getting unexpected values in your LVM file is because you do not have indexing enabled on your timed loop.  Your loop will run the specified number of times and only write the latest value to the outside terminal of the loop.  To remedy this, you should either consider using a Build Array and/or Append Signals with Shift Registers inside of your loop to build up your signal to write to the LVM file, or enable indexing on the wire terminals on the right side of the loop (right click the data coming to the right side of the loop and select "enable indexing".  This is the same operation as using a build array with a shift register inside of the loop -- i.e. each iteration of the loop will add to the existing data, and in the end dump the resulting array to the Write LVM File VI.

Hope this helps, please let us know if you have any other questions!

Regards,

Travis M
Applications Engineer
National Instruments

[sdonah2]

Will this correct the problem that all the digital signals are recorded in one col, instead of a digital signal for each col.

Thanks

Scott

[Chris_Cilino]

sdonah2,

Enabling shift register won't affect HOW the data is writing. It will only affect how MUCH of the data is written. By using the enable index function, you write the data from each iteration of your loop, not just the last iteration's data.

 As for wanting the digital data in a row instead of column, the Write to LV Measurement vi was designed to place one signal in each column. So each channel from your DAQ device will be placed into its own column. If you'd like to read that data back out of the file and transpose it (switch a column to a row), you can use the "transpose.vi" when reading the digital signal from your file. But be aware that this won't change the .lvm file.

Best Regards,

Chris C

Applications Engineering

National Instruments

[sdonah2]

I think you misunderstood my question. The all 7 lines of digital data is being placed into one col, instead of 1 column per channel.

thanks

Scott

[sdonah2]

I inserted the shifft registers, but now I keep getting error 20315, sying that

Possible reason(s):

Analysis:  The waveform dt parameter is <= 0.

Complete call chain:
     ma_Check Waveform Timing.vi
     ma_check Time History Signal Continuity.vi
     ma_Basic Averaged DC-RMS no state.vi
     Basic Averaged DC-RMS for 1 Chan.vi
     Analog-SubVI.vi
     Multi-Function-Synch AI-Read Dig Chan4.vi

[sdonah2]

Please Help

I would like to be able to save all data to one file, in the way that the digital data is saved. So I need to be able to save the analog data the same way I save the digital data, with the same time stamp for each, thus synchronized.

Also, when I use multiple samples per loop iteration, the digital data time stamp goes to zero after a certain amount of samples have been taken. It still takes digital data, but the time stamp after a certain point remains zero.

I have tried and tried to get this vi to work, (like a month), and I can not. Can you please edit it with the proper corrections, because nothing I try works and I can not afford to spend any more time on it.

Thanks for your help

Scott

I could not get the attachment to work so I just provided a link.

https://netfiles.uiuc.edu/xythoswfs/webui/_xy-11759284_2-t_1NA8BhvD

[Marni]

Dear Scott,

Putting the two writes in the same while loop doesn't really synchronize the two inputs. If you want the two signals to be synchronized I recommend upgrading to a new M Series board. They have correlated DIO that synchronizes analog and digital lines.

When you talk about the timestamp, are you talking about the dt of the waveform or the tick count? Please clarify on what you mean. Have a great weekend!

Sincerely,

Marni S.