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Data channels are randomly assigned at the start of a test, why?

I have a DAQPad 6015 (USB) and use Signal Express V 1.0 software. I am recording data from 8 channels at 0.5 Hz. When I start a test the channels are randomly assigned the in which they are written to the ASCII file. CH0, CH1, ... CH7 may be written to the file as CH2, CH5, .. CH7 the first time and then CH1, CH3, ... CH2 the second time. I have tried both setting up DAQPad with and without MAX.

Do you have any suggestions?
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Hello Pguiet:

I tried to reproduce your issue with little success. I tried to save 8 channels to an ASCII file and it seemed to do it perfectly. Did you make sure to click on the 'Include Signal Names' option?

Has this ever worked for you or has it always given you this problem?

Furthermore, are you using SignalExpress VIs in LabVIEW or are you just using the SignalExpress stand alone program?

Jaideep J
Applications Engineer
National Instruments
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I am running Signal Express and do not have Labview. I can not find "Include Signal Names" as an option or otherwise within Signal Express or Max. I can rename the channels but these name do not show up in the ASCII file. This is a new system and these first tests.

I have attached the workfile RC1000W 02Mar05.wbp renamed RC1000W 02Mar05.txt
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The project you included was very helpful. The reason is that SignalExpress steps which have no inter-dependencies are run in "parallel". Given that fact, the scheduling of steps that can run in parallel is not deterministic. So eventhough all eight of your Save to ASCII have a dependency on your NI-DAQmx Acquire step, they have no dependencies between each other. So although it is guaranteed that your eight Save to ASCII steps will not begin executing until the NI-DAQmx Acquire step has completed, it does however mean that once the Acquire step is complete, all eight of your Save to ASCII steps will try running (at the same time) and there will be no guaranteed order of execution for those eight steps.

The workaround: Have your eight Save to ASCII steps save to different files, and then find a way to merge the files, either manually or programmatically. To do it programmatically, I've created a User-Defined Step for you using LabVIEW 7.1 that will do the job, and modified your project to include the step and changed the test file names.

The solution: SignalExpress 1.1 has upgraded the Save to ASCII step. It now has the ability to write multiple signals (of the same type) to a file using a single Save To ASCII step. This would mean that you could replace your eight steps with just one that would do the job.

I'm including a zip file which contains:
1) MergeTextFiles.llb - the user step VI.
2) RC1000W 02MAR05 modified.wbp - the modified project.
3) RC1000W 02MAR05.wbp - your original project.

Just open the modified project, open the NI-DAQmx Acquire to select your device (instead of mine), and click Run Once, then wait for your Acquisition to complete. I've new files save to the same location yours did.

I hope this helps...
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Okay, having a different text file name for each ASCII step appears to be working. This is cumbersome but it works. Thank you.

You mentioned SignalExpress 1.1 and I have 1.0. How do I get the upgrade? I can not find it on NI.com website.
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You can go online to NI's Software Upgrade Advisor and request a free SignalExpress 1.1 upgrade.
http://www.ni.com/advisor/ -> Software Upgrade Advisor

I believe that SignalExpress 1.1 becomes available around March 25, 2005.

For information about the new SignalExpress 1.1 features, there is a list on the "What is SignalExpress" web page at:
http://ni.com/signalexpress/whatis.htm
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