Monday, September 16, 2013

Cleanliness is next to godliness

Noise- electrical noise. One of the banes of the electrophysiologist. It turns your recordings to laughable 60 cycle garbage, that you'd be embarrassed to publish. It turns your days into fruitless searches for impossible to find ground ground loops.

Some of the most pernicious sources of noise I've had resulted from old spills of salt solutions that I thought I'd cleaned up. One time the saline seeped between the air table and a post holding the manipulator and headstage. That created a weird acoustic pickup that was near my voice's natural frequency. Took me a long time to find that one.

Another annoying place that salt can build up is the pipette holder itself. A little excess internal solution at the non-tip end of the pipette can get into the holder, causing havoc. I haven't seen that lead to overt 60 cycle noise, but rather an increased RMS noise that makes single channel recording more annoying that it already is.

To get around that, a good dip in the ultrasonic cleaner can do wonders. I fill up the cleaner with a solution with some detergent (1% ContRad works well). The detergent improves wetting of the objects you're cleaning, and reduces microbubbles-which prevent effective cleaning. Degas the solution by running the cleaner for 10-15 minutes, then immerse your disassembled holder and bath in the solution. Let it run for ~10 minutes, wash your stuff a few times in dH20 and you're good to go.

A cool way to test if your cleaner is working well is with a pencil mark drawn on the frosted end of a glass slide: