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NI-DAQmx - Multiple Channels Data Aquisition


@obzy98 wrote:

And when i say 0V i mean disconnecting it, not setting it to 0V, so it's technically an open circuit.


That is your ghosting problem then.  When you just disconnect, you have no path for the ADC's setup and hold circuit to discharge.  A simple fix would be to add a 10k resistor to ground for all of your channels after wherever it is that you disconnect.


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For problem 2, i tried that, only difference is that the wait time made it produce 5 Samples per second instead.


The sample clock and the wait time in a sample read loop are not linked. The sample clock is the sample clock, it is always running in hardware (the USB instrument) loading samples into the buffer. You don't need to, nor should you try to time the sample rate in software. Your job in labview is to go in and read samples out of the buffer so it does not overflow. You can read the samples out of the buffer an order of magnitude or two slower than the sample clock is running. For example the sample rate is 100S/s and you read the buffer every second, so every time you read the buffer you get ~100 samples that each have a dt of 0.01 s

 

Also don't try to calculate the S/s rate, you define this with the sample clock, you should trust it. 

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@crossrulz wrote:

@obzy98 wrote:

And when i say 0V i mean disconnecting it, not setting it to 0V, so it's technically an open circuit.


That is your ghosting problem then.  When you just disconnect, you have no path for the ADC's setup and hold circuit to discharge.  A simple fix would be to add a 10k resistor to ground for all of your channels after wherever it is that you disconnect.


Here is an article for OP to read about open channel behavior - https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P6TeSAK&l=en-US

 

Santhosh
Soliton Technologies

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