BNC 2090 crosstalk

[clarksonphysics]

I am having issues with a BNC-2090 and a PCI-E 6052E card causing crosstalk or ghosting between channels. I am trying to measure the voltages of two sets of sensors on seperate channels but each set of sensors interfere with each other. I have tried following the suggestions from national instruments but they have not solved the problem. I have also tried another set of the same equipment but it appears to have the same problem. I have attached two pictures. One is where channel 2 has a signal and channel 1 does not but a signal appears without one being supplied and the other is the other way around.

[KyleTTU]

Hi clarksonphysics,

Can I ask which suggestions you tried in the ghosting article?  Did anything alleviate some of the crosstalk?

Regards, 

Kyle S

[KyleTTU]

Hi clarksonphysics,

Can I ask which suggestions you tried in the ghosting article?  Did anything alleviate some of the crosstalk?

Regards, 

Kyle S

[clarksonphysics]

I have treid 1 and 2, 3 I have not done, 4 is not possible with my setup, I do not have a high impedence channel for 5 and 6 I do not know how to do or if it is possible.

[KyleTTU]

Hi clarksonphysics, 

How high are the impedances on channels 5 and 6?  Is there anyway you could incorporate something along the lines of a Unity Gain Buffer to lower the impedance?  Also, about how fast are you sampling all of the channels?

Using a Unity Gain Buffer (Voltage Follower) with a DAQ Device

http://zone.ni.com/devzone/cda/tut/p/id/4494

Regards, 

Kyle S

[clarksonphysics]

I think my last comment got misread due to a missing comma. I don't have a high impedence channel. The 5 and 6 were referring to the fifth and sixth suggestions in the article.

I am measuring at 100,000Hz which is the max, normally but I have tried decreasing it to as low as 100 which made no improvements.  

Both of my inputs are an array of sensors that go into one channel and I would like to try the unity gain buffer but unsure if I would need one on each sensor or just one on the array.

[KyleTTU]

Hi clarksonphysics,

Have you tried limiting to one sensor per channel and see if that affects the measurement?

Regards, 

Kyle S

[clarksonphysics]

I have tried seperating the sensors and only having 1 of each running at a time and each of those having their own channel but this does not help. I am not able to try this at full scale because I have 30 of each type of sensor in each array.

[KyleTTU]

Hi clarksonphysics,

Is it a possibility you are operating outside of spec for this device?  This does not sound like normal behavour so I'm curious if it is acting poorly because of either the voltage or current of the signal you are sampling.

Regards, 

Kyle S

[clarksonphysics]

I do not believe I am out of spec. The voltages I am measuring is between 0 and 5v and the current is under 1 amp. This is also not the only experimental setup that has had this problem either and I have tried another daq card and bnc block that made no difference.