for some weeks now I ame faced with a problem with two Waters 996 PDA-detector in our lab. The baseline of these PDA's is going up and down in about 8 min. these symtomps are there pumping elluens and without pumping elluens. When I monitored the baseline of the two PDA's at the same time, the baseline's moved up and down at the same time and when I moved one of the PDA's to an other building the baseline was stable so I think both PDA's are working fine. Recently the UV-spectrum also showed " humpy" figure. the humps where about 3 nm apart. I don't if this problem is related tho the first one.
So, what might be wrong? people sugested that the power-suply of our lab may be the problem. Any one knows how to test this?
Somebody else sugested magnatic interferance. How do I test this?
Any other sugestens welkom.
thanks.

My guess would be the power supply. To test, get a surge-protector to put between your current power supply and the detector and see if the problem disappears.

Another guess is that the PDA's are located in close proximity to air conditioning vents.

We have 2 Waters 996 PDA detectors which behave exactly as the original poster described, so badly in fact that the Waters Tech could not get the detectors to pass IQ/OQ without switching the air con off. We had conditioned power thru UPS so power supply should not have been a factor in the wavy baseline in our case.

Funnily enough, our UV-vis detectors in the same room don't show the same behaviour. Anyone know why?

dear phil,

thanks for your mesage. Did you figure out was coused the problem. was it a magnatic interference or was it temperature based?