Testing a device in labview? how?

[Canucks.canucks]

I just used differential because I didn't know how to measure output of analog to digital boards (which is the input to SCB-68). The test is pretty much useless.I just wanted to show the devices. Is there a way to test the DAQ with my signal instead of simulated signal? ( sorry if my questions are stupid!)

[TroyK]

Just trying to verify exactly what your setup is before attempting to give advice.

This my understanding from what you've described...

The waveform in your attached image (test2.png) is what you might expect to see if you used an analog input to sample a digital signal at a slow rate.

If my understanding above is correct, then you should probably change your setup.  While it is possible to sample a digital signal with an analog input and process it to extract the data, it is probably not the easiest way to get the data you want.

You may be able to bypass the "AD board" completely.

Who wrote the "LabVIEW program" you mentioned earlier? Do you have the source code? Can you attach it? It might be useful to see what kind of signal the program is expecting and how it is processing it. Or are you just using MAX to check the output?

[Canucks.canucks]

You are absolutely right . When we called NI in the morning they told us that we don't need to use AD to convert analog to digital . The problem is we can't directly connect the amplifiers to the computer or scb ( the connectors are different) so we used the boards . It's been working for the last 7 years and i don't know why we have been experiencing so much noise lately 

[Canucks.canucks]

Labview code was written by our previous engineer . I'll teach it tomorrow 

[TroyK]

So it suddenly stopped working? Then you just need to work out what changed, not redesign the system.

Do you know what the signal looked like before? Could a connection have come loose? A ground connection perhaps?

[Canucks.canucks]

Yes ! All of a sudden we get lots of noises when we collect data ! Literally nothing has changed ! So odd

[TroyK]

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CanucksGirl wrote: ...Literally nothing has changed !...

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Everyone says that until they work out what has changed. Something must have changed, otherwise it would still be working. You just have to work out what it is.