It seems to be a consequence of a ground loop . (Or maybe power
In case of ground loop pls. see the following:
Ground loop problems and how to get rid of them:
If you have any question do not hesitate to ask.
abbarnet at dal.ca (ABarnet) wrote in message
news:<7bad14f2.0405260739.74860979 at posting.google.com>...
> Help please!
>> I am having serious problems with noise in a PAM 101/102/103
> fluorometer (Walz). The normal noise in the signal ranges about +/-
> 0.015V measured at 1.6kHz with the gain/damping/etc settings I'm
> using. This goes through a strange low-frequency sinusoidal pattern
> in the signal followed by an increase in the noise to +/- 0.20V
> measured at 1.6kHz. The signal then can either remain noisy, or
> slowly decrease in noise back to a normal level on a time scale of
> 30min to hours. This noise comes and goes unpredictably and I can not
> do anything to induce or get rid of it (ie. wiggle conntections, find
> breaks in wires, bad grounds, etc.).
>> Has anyone seen this problem before or had similar problems with their
> instrument? Any insights?
>> I have ruled out the posibility that it is stray light into the
> photomultiplier detector. Also, analysis of the output shows the
> signal noise is not at a frequency of 60Hz, so I am assuming it is not
> electronic interfearence, but I have not totally ruled that out. I am
> in the process of doing things like replacing the BNC cables and
> trying to make sure everything is shielded. I have also verified, by
> hooking up a chart recorder, that the output to the computer is what
> the PAM is telling it.
>> Thanks for your input!