Hello Hitesh, and thanks for your reply.
I accept the samples per second issue in that the sampling could take place on any part of the sinewave and give error results over 1 single scan. I'm currently using a (so called, real time) software spectrum analyser via a USB connection. I get around the sampling issue simply by using the peak/hold function and allowing the system to make loads of scans - like in a loop til I stop the scanning. In a fairly short time the screen displays a fully built spectrum analysis curve which I can then print. Not ideal, but it does work!
Eventually I will need to record 5 or 6 chans of data which was one of the reasons I thought the logger might be better for me than the Picoscope. As mentioned in the first post, I could RMS to DC convert the AC signal if it would help.
But if your software can do the peak/hold function of many scans, that **might** work better for me, because I am going to need to record those multiple analogure chans as the project develops. I just can't afford a multi chan, analogue Picoscope.
If you've further advice I'd be obliged.