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USB 6009: DAQmxSetAIConvRate causes error -200452

Thanks for your input, Brian.  My current solution is a variation of solution #4 in the article (arrange signals to minimize voltage swings between channels).  My arrangement duplicates inputs so there is no voltage swing for the second input in each pair.  But this cuts the number of available channels in half.

I was hoping to use a variation of solution #2 in the article (reduce sampling rate and increase interchannel delay to allow enough settling time for the amplifier).  Reducing the sampling rate doesn't seem to help, it as far as I can tell there's no way to increase the interchannel delay on the USB 6009.  Is there any way to update the firmware to change the delay?

BTW, I was using a 10K potentiometer in the test I described previously.

Mike
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Hello Mike. 
 
There is no way to update the firmware on the 6009 to change the delay.  I am interested to know the voltages on each analog input channel.  There should be a way to connect these in an order that does not introduce ghosting on surrounding channels.  Also, what is the source impedance on those channels? 
 
Brian F
Applications Engineer
National Instruments
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Hi Brian,

The way I have things connected now (one signal connected to two consecutive channels) seems like the best option.  Unless of course my 6009 is faulty and needs replacement.  Two of my inputs come from a signal conditioner which probably has a low output impedance, although I don't know for sure.  One input is the voltage across a 1K resistor in a voltage divider with a 10K resistor.  The fourth channel is extra and unconnected for now.

Anyway, did you get a chance to check for ghosting in the test I described previously?  This was a two-channel test with one input wired to the 2.5V reference and the other input wired to a 10K potentiometer connected to the 5V reference.  I saw spiking/ghosting with this setup and the sample C program (modified slightly to print out more data points).

Thanks,
Mike
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Hello Mike. 

I have tested the USB-6009 with that exact configuration and have not seen any ghosting on my channels.  I connecting AI0 to the 5V source and AI4 to the 2.5V source.  I also tried the combination of AI1 and AI5 as well as AI0 and AI1.  All of these tests, when viewed in the MAX test panel, came back without any ghosting.  It would certainly help if you had another USB-6009 and could test that one to see if there was a difference in the readings.  Since I am not able to replicate the issue that you are seeing, I am starting to suspect that something may be wrong with the actual hardware.  Running a test on your exact inputs with another 6009 would certainly shed more light on the issue. 

Brian F
Applications Engineer
National Instruments

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Thanks for all efforts, Brian.  Did you happen to test things with the C example?  I used the code in
   /NI-DAQmx Base/examples/ai/contAcquireNChan.c .

--M
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Hello Mike. 

I have not done this test yet since I don't see why C code would give different results than what I saw in MAX.  However, for completeness sake, I will test this today and keep you updated of the results I see. 

Have a great day!

Brian F
Applications Engineer
National Instruments

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