Low sampling rate with BNC-2090

[yonikup]

Hello,

My name is Yoni. I'm trying to record field potentials from a rat brain. This is the equipment that we are using:

1) Amplifier - NPI SEC-05LX (http://www.npielectronic.com/content/downloads/SEC05LXmanual.pdf)

2) Digitizer - National Instruments BNC-2090

3) Data acquisition card - National Instrumets PCI-MIO 16E-4

4) Computer - Pentium 4 2.8GHz (Dell Optiplex GX620)

5) Acquisition software - Axograph.

Our problem is that when we use the above configuration the traces look very poor, like the sampling rate is really low or there is a very low-pass filter (It just looks like a flat line with "square" noises...). It actually doesn't matter what sampling rate we enter in the acquisition program or what filter we use on the amplifier, we always see the same thing. When we tried another digitizer (Heka ITC-18) it works fine. So at least we know the amplifier is OK. Since we need to work with the BNC-2090 we want to try and fix the problem. One of the possibilities is that somehow we are losing data when it is transferred from the digitizer to the acquisition card (using a 68-pin cable) or when the data is transferred from the card to the computer (of course, it could a problem with the acquisition software and I will check that too). I guess I have two questions:

1) Do you have any idea what can cause the problem?

2) Since it could be a card problem (or a compatibility issue between the software and the card) is there any adapter/device that can convert the 68-pin to usb so I can bypass the card?

Thank you for your help,

Yoni.

[Dennis_Knutson]

The BNC-2090 is not a digitizer at all. It is just a dumb terminal block so I don't understand your question.

[yonikup]

My questions are:

1) Why, in your opinion, do the traces on the screen look like the sampling rate is very low and are not sensitive to changing the filter on the amplifier or changing the sampling rate on the acquisition program?

2) Is there any way to bypass the PCI-MIO card so the data is transferred from the BNC-2090 to the computer through a USB port?

Thanks,

Yoni.

[crossrulz]

As Dennis already stated,  the BNC-2090 is just a terminal block.  It has no digitizing capability.  It is simply a way to connect a card to the outside world via BNC.  The interface between the DIO card and the BNC-2090 is a 68 pin cable.  I don't know of any USB devices that will use this type of cable.

[Dennis_Knutson]

I'm really sure what this heka is but if it does some sort of signal conditioning, that could explain the problem. Assumimg you were also using the DAQ card when you say it works fine. You obviously are mistaken about the capabilities of the 2090.