Hi, I have an application where I am measuring ion current using a Faraday cup in a vacuum chamber. For our measurements, we have a Keithley 616 picoammeter and it does pretty well but we also have quite a bit of noise. I believe the noise is 60 Hz related because if we shut down nearby equipment the noise goes away and that equipment is 480 V industrial machinery. Unfortunately, we need to take measurements on a regular basis and its not feasible to shut down equipment on a regular basis in a production plant. I was hoping it might be possible to make a 60 Hz notch filter to remove some or most of the noise. The UAF42 is an active filter that might be useful and it only has about 10 pA typical input bias current. Our measurements are in the high nanoamp to microamp range which is well above the input bias current range of this active filter. Any recommendations on using this filter in such a setup? Are there other active filters or possibly passive filters I should also consider?
One more question, my picoammeter is essentially functioning as a transimpedance amplifier (converting current to voltage) so in general is it possible to use this active filter ahead of any transimpedance amplifier? Or is there a passive filter that might be more appropriate?
Regards,
Scot
