Checking the quality of your AC

That's interesting that you want to see if you have a problem with your AC. I think the power conditioner manufacturers just want you to assume that you do. And also assume that all of your audio equipment can really sound better if you use their power conditioner. If you could borrow an oscilloscope for a couple of days, that would be a good way to check it out. That reminds me of one time when I was hooking an oscilloscope probe up to a wall outlet and I connected the probe ground to the positive terminal of the outlet. Poof, flames in my face. Be careful making measurments on wall outlets!

Zaikesman, your meter is telling you the average voltage on the line. The thing you can't tell is wether there is any superimposed noise on the line or fast transients, etc. You really need an oscilloscope to see if there are any problems like this. In my house, there just wasn't anything to see.