Multifunction Analog output/input

[vishnu7]

I am using USB X series 6356 for my experiment. I send a tone pulse through Analog output channel to an actuator.

And receive response signal from a sensor to an Analog input channel .I have include a screen shot of the VI. 

The issue is, I get the output signal in the response signal as well.

If I send (through output channel) a 10 KHz tone burst which starts at t = 0.

I see the Tone burst in my input channel plot as well (at t = 0).

Please, let me know if I'm using the right VI (I build it based on multi-function-synch AI-AO VI from the examples).

I use the loop to remove the 60 Hz noise signal(by averaging over 100 times). 

[Leah-L · Accepted solution]

Hi Vishnu7,

From what you are describing, it seems like you might be experiencing some ghosting or crosstalk on your analog input channel. Take a look at this knowledgebase article and see if this matches up with what you are seeing. 

http://digital.ni.com/public.nsf/allkb/73CB0FB296814E2286256FFD00028DDF

[vishnu7]

Does ghosting occur between Output and input channels? Sorry for my ignorance, but the link suggests ghosting exists between Input channels.

And does the VI, I'm using perform the task of synchronizing Output and input channel. Want to make sure everything is ok with the VI.

[Leah-L]

Hi vishnu7,

You are right. Ghosting specifically will occur between analog input channels as a result of a high source impedence. A more general term for what could be happening is crosstalk. Let me provide you with some more resources. 

http://digital.ni.com/public.nsf/websearch/B9BCDFD960C06B9186256A37007490CD?OpenDocument

http://www.ni.com/white-paper/3344/en

From my point of view, I don't think that this is related to your VI. I believe this to be a hardware problem. One thing that I would like to be very aware of is how we have our signals grounded. We need to make sure we don't have any ground loops in our system. 

Take a look at Table 1 in the document entitles "Field Wiring and Noise Considerations" Depending on whether your signal source is floating or grounded, this will affect what kind of input configuration we use. Are you currently using Differential, NRSE, or RSE?

[vishnu7]

I have not connected anything, so its in default mode. I have attached a wire diagram of my experiment, hope that helps

[Leah-L]

vishnu7,

If you don't have anything connected to your channels, it is expected that you would see crosstalk from the other channels. You should expect to read 0V only if you are actively driving 0V to that channel. You can't expect a specific voltage to be read by the channel unless you are specifically driving that voltage to the channel. 

This article explains why this happens. http://digital.ni.com/public.nsf/websearch/4E9B8B3F8FD3A31B862562B5004EA1D9

[vishnu7]

I was refering to the connections in the block diagram."Differential, NRSE, or RSE" connection to the create channel VI. 

I think u are referring to the physical connection (leads) to the daq ports.

[Leah-L]

Hi Vishnu,

Sorry for the confusion. Make sure that your physical connections match up with how you have your input configuration set up. For example, if you are using a differential configuration, make sure your are wired to AI+ and AI-, and if you are using an RSE configuration, make sure that you are wired up to AI+ and AIGND.

Leah