Problems with signal when going from BNC to alligator to BNC

[babyloniantg]

Hi,

   I am trying to get a signal from a waveform generator, run in through a circuit, and then have it go to my DAQPad board so that I can display it on a computer. If I connect the waveform generator to the DAQ board directly through a BNC cable then the signal shows well on my LabView program. However, if I try using a (homemade) BNC to alligator cable and connect it to another alligator to BNC that connects to the DAQ board, my signal gets screwed up. The reason why I am doing this BNC-to-alligator-to-BNC setup is that, like I said, I'm eventually going to include a circuit in between and I planned on connecting to the inputs and outputs of the circuit with alligator clips. Right now, I was just trying a preliminary test without the circuit to see if I could even carry the signal this way. I'm not sure why this is happening since the only thing I'm doing is break the BNC cable and reconnecting it with alligator clips. The only thing I can think of is that noise is screwing up my signal, but my graph in LabView shows up just like a constant value (as opposed to a sinusoidal wave, which is what I want). I'm relatively new to building circuits, so I might just be making a silly mistake. Any help is greatly appreciated.  

Message Edited by babyloniantg on 06-29-2006 10:56 AM

[AnalogKid2DigitalMan]

Is the constant value zero? That may indicate that you are shorting out the output of the generator.

If it is not zero, then maybe you have an open circuit on the center conductor or the shielded braid.

If you have access to an ohmmeter you can test your connection for opens and shorts.

[MJF]

As suggested, it could be bad cables. I would suggest buying the type you need from a vendor like Pomona Electronics that specializes in test cables, leads and adapters.

http://www.pomonaelectronics.com/index.php

From your description, I am assuming you want something like this:

http://www.pomonaelectronics.com/images/large/4531.jpg

Another option if you can do it is to put BNC connectors on the circuit card, that way you will likely get the best signal integrity.