High Speed Data Logger (DAQmx)

[AndreasWerdich]

I want to use the DAQmx version of the High Speed Data Logger which is avilable for download from the NI website:

http://zone.ni.com/devzone/cda/epd/p/id/3441. The vi streams a specified number of samples at a given rate to a binary file. It also creates a comprehensive header with date,time,scanrate,channel names and a user header.

The file is called 4026.zip: ftp://ftp.ni.com/pub/devzone/epd/4026.zip

Problem:

It is not possible to read the binary file with the High Speed Data Reader example (legacy):

http://zone.ni.com/devzone/cda/epd/p/id/3701. This program is available as a labview example, "high speed data reader.llb", 

here: ftp://ftp.ni.com/pub/devzone/epd/high_speed_data_reader.llb. But it does not work with the DAQmx version of the Logger.

The output date is corrupted and the data shows all zeros, so that I believe that the header information is not extracted correctly. Question:

Is there a binary reader available for binary files created by the "High Speed Data Logger (DAQmx).vi"?

Did the Engineer who wrote the "High Speed Data Logger(DAQmx).vi" write or modify a binary reader accordingly?

Please let me know which program I can use to read the data.

I would really appreciate any help!

Andreas

[Abhinav T]

Andreas,

The High Speed Data Reader you are using assumes there is a property set - scale multiplier, something that is brought over from the older Traditional DAQ driver. If this property is not set (as is with the High Speed Data Logger for DAQmx) the data is multiplies by zero. If you changed the multiplier in the top part of the while loop to be multiplied by one (1), you will get the original data (without any scaling)

Hope this helps!

Abhinav T.
Applications Engineer
National Instruments

[h3l]

Hi, I am a new user with Labview. I need to read a high speed signal. My devices are a PCI 6133 and BNC-2110. The labview version is 8.5

This signal has a frecuency between 1KHz and 10KHz and last less than 1s. I am using the high speed data logger and it seems to work.

I am having problems with the high speed data reader.  When I try to read the signal, it seems to be 0. I don't know what can I do, as I checked the block diagram but I can't find or more exactly I don't know what is the multiplier  in the top part of the while loop.

 Another possibilty that I have checked is to use the signal express but I think that it is not fast enough. I tried to set it to read high speed data. I followed the advices of another comment (optimizing labview signal express for high speed or high channel count logging) but when I set high rate, the programs crashes and it has not enough memory.

Also, I don't know if I can read with the signal express the data acquired with the high speed data logger.

I hope you can help, as I need to find the solution to start working.

Thanks in advance. 

[Now_With_Underscores]

Hi H3I,

I've attached a screen shot showing the issue.  If you delete the bottom leg that comes in from 'scale multiplier' and replace with a constant of 1, then the data will stream properly.

Message Edited by Knights Who Say NI on 12-12-2008 05:11 PM

[h3l]

Hi, John S

Thank you for the answer. I made the changes and now it reads something. Anyway I discovered how to work with signal express and I am using it as I can set configurations that I need.

The fact is that I am trying to record the signal from a specimen that is subjected to a cyclic load until it breaks. As I don´t know when exactly it breaks, I set leaving the window as recording condition but I would like to record about two seconds previous to this condition. Is that possible? 

Thanks in advance.

[Jason_D]

HI h3l,

You will want to look into pretrigger samples.  You can do this by adding the Trigger step which is under Execution Control.  It doesn't appear that this can be set to a number of seconds but you can set it to how many samples you would expect to acquire in that time.

[mooseo]

Hi,

I'm having a different problem with the high speed data reader... it uses the pre-mx vi AI Hardware Config. Since I have 8.6, this won't load properly. Is there a DAQmx vi that will get the same info (it's looking for group channel settings and number of channels in file). 

thanks,

mike