Crosstalk among Analog channels

[MogaRaghu]

The setup is this :

1. Card is PCMCIA 6024E.
2. Software is LV 7.1 and all reads are with DAQMx functions.
3. 6 analog channels configured in differential mode ( AIN_0 to AIN_5)
4. Connected to the card via BNC2110 connector.

If I connect only one channel to a signal, it is reflected in all the other 5 channels at different levels.

I do know that I can solve this problem by two means :

A. Ground the unused channels to AIGND.
B. Use alternate channels with one grounded channel in between two active channels.

In my case since I need all 6 channels at times, so option B does'nt exist.

Question is, can something be done in the software without resorting to option A.

I have attached the snap shot of my problem. The straightline plot is the channel that has a signal on it and the other "followers" are free channels. At 15:49:43 I made the active channel zero and you can see all of them dropping to zero. Then I started another channel and all of them pick up !

Kindly help solve this.

[SE_Hoard]

I would be interested in any solutions to your problem also. I am experiencing a similar problem with my setup. I am using a PCI-MIO-16E-10 to acquire data from a SCXI-1142 filter card. When I input a signal on CH0 it also appears on the other 7 channels. I am not sure if this is happening because my DAQ card is set up for RSE input rather than differential. However, if you are seeing the same thing in your setup, the solution to your problem would probably also work for me.

[johnsold]

Always ground or otherwise terminate all unused channels to a low impedance and low noise source. This kind of crosstalk is quite common if the inputs are not terminated.

If the source impedance of some of your sources is high (megohms), you may see the same effect when other channels are driven by low impedance sources. The only fix for this case is a buffer amplifier on the high impedance lines.

Lynn

[MogaRaghu]

---

@SE_Hoard wrote:
I would be interested in any solutions to your problem also. ... When I input a signal on CH0 it also appears on the other 7 channels. ....

---

I was searching the tutorials and application notes on the NI site. Located this PDF which discusses the aspect of amplifier settling times in a multiplexed front end of a multi channel DAQ setup. Just read through the recommendations and see if they can help to reduce crosstalk in your case :

http://zone.ni.com/devzone%5Cconceptd.nsf/webmain/B9B5D37A04C772B58625686500695C20/$File/AN045.pdf

Raghunathan