Query about NI 9234 & NI 6210

[Sauvik]

Hi,

We are students from Oklahoma State University, working on a project using LabVIEW. We are trying to acquire the EMG signals from Human hands using a MyoScan EMG Amplifier from Thought Technologies & a DAQ board from National Instruments. We are trying to use NI 9234 & NI USB-6210 as the DAQ boards.

However, for the same EMG electrodes' configuration, we are getting good results using the NI 9234 & not so good results using the NI USB-6210. We have two NI 6210 boards with us.

We want to know the reason of this difference & how can we fix the problem with the 6210.

We are attaching the Screen-shots of the outputs that we are getting.

Thanks,

Sauvik Das Gupta

[Sauvik]

Also to let you know we are following the NI 6210 pinout configurations given in the datasheet in order to connect our Analog Input channels to the DAQ.

We are using Voltage as our Analog Input in this case. The datasheet that we are following is attached.

Thanks,

Sauvik Das Gupta

[Rohama_K]

The NI 9234 is a DSA module and so it cares more about resolution, sacrifices accuracy and favors frequency content rather then DC precision. Plus, there are a lot of other differences between the two devices. For example, the USB-6210 has 16 bit resolution versus the NI 9234 has 24 bit resolution. Same goes for the sample rate for the two devices. 

With that said, you should still be able to get an EKG signal with the 6210. What is your input voltage range?

How is your code set-up to acquire the data? Could you attach the code you used for both modules?

[Sauvik]

Hi,

Thanks for your reply. I want to make some points:-

1. We are not acquiring EKG signal. We are acquiring EMG (Electromyography) signals in our project.

2. Our Input Voltage range is in Millivolts. We are amplifying the Raw EMG with the MyoScan EMG Amplifier from Thought Technologies and then trying to acquire the Amplified signals through the USB-6210 DAQ.

3. We are trying to do this data acquisition either by LabVIEW or an ANSI C code. I am attaching both the codes for your reference.

Thanks,

Sauvik Das Gupta

[Steve.J]

One of the other big differences between the USB-6210 and 9234 is that the 9234 has an isolated input.  Judging from the noise that you are seeing in your 6210 picture, you seem to have a grounding or input configuration problem, possibly a ground loop and this is leading to lots of line frequency interference (just a guess from looking at the signals).  The isolated input on the 9234 inherently prevents this kind of problem.

Make sure that you have the 6210 setup in differential mode which creates a (+) and (-) input for each channel (and halves the number of analog input channels). You may be able to get away with NRSE mode, but try differential first.

Read this DevZone article for more information on dealing with ground loops and input modes:  http://zone.ni.com/devzone/cda/tut/p/id/3394

Good luck!

Steve