USB 6009 and TDMS write

Dear all!
I'm using USB-6009 device to adquire data from a physical channel. In the following vi, the number of samples to be adquired is set to 1000, with a 100Hz rate. Therefore, as I understand, the number of samples that should be read inside the while loop where DAQmx read is placed should be 10 for each iteration. However, I've tried to store this information in a TDMS file and I'm getting less number of samples as expected. I wouldn't like to lose any data.
I've read overthere that the USB-6009 is a software-timed device, so, can this be the reason of this anomaly? Moreover, if I analyze the adquired samples using DIAdem software, I see some samples are being repeated. In this case, am I overwriting some data and reading past values?
If I need to replace my data adquisition device with a hardware-timed one, which one should I get?
Thank you very much in advance,
Miren
Attachments:
USB6009_TDMS.vi ‏25 KB

When you run the sample clock in "Continuous Samples" mode, the # of samples only determines the buffer size. This is outlined in the help for that function.
As a result, you have nothing pacing the internal loop: If there are samples available when it reaches the DAQmx Read, it passes out as many as are available in the buffer. You might get 1, 2, 100; it depends on how long the other operations in the loop take.
In general, DAQmx loops like this can be paced either by time or by # of samples. Looks like you want sample pacing: wire the number of samples you want to collect to the "# of samples per channel" input of the DAQmx read. Then the loop will wait at the daqmx read until that many samples are ready, and then it will proceed.
-Barrett
CLD

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Aaron T. wrote:
Hello, I just received a USB-6009 multifunction DAQ device along with DAQmx Base for use on Windows XP with LabWindows/CVI ver 7.1. Both the 6009 and DAQmxBase are successfully installed however I have several questions, I hope I am missing something obvious: 1. The Task Configuration Utility is not needed for use with LabWindows/CVI? I believe I read this in the Getting Started Guide.
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Thanks in advance for the assistance,
John Weeks
WaveMetrics, Inc.
Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

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Test1.vi ‏213 KB

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Glucose Sensor Developmental VI.zip ‏77 KB

I figured it out. In processing case, I was reading from the same group eaverytime. so the all the processign data was same. All I had to do was to get the current group value from the property node and wire it to tdms read function.
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Message Edited by Troy K on 06-06-2008 02:36 PM
Troy
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