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Yes I realize the danger with 240. And I also realize the steep learning curve.
That is the way I've learned a lot of things and I guess I enjoy the challenge.
I'll read up on precision rectifiers.

Ok I'll use a transformer. the question that leaves me with though is how do I know what the measured voltage is in relation to the ADC reading. Say I have everything set up so the input to the ADC is 2.5VDC when the input to the transformer is 240VAC. Now when the ADC reads at 2VDC how do I know wh...

So what is the isolation needed for?
And also I'm hearing two options, one is just run it through a rectifier and voltage divider and the other is use a step down transformer.
So I don't know what to do.
Does the transformer act like a voltage divider with a ratio?

It's US 240 if you know what I mean. It's coming off of a stepdown transformer with a center tap and so from the two lines two the center tap (ground) is 120VAC. So I don't know how I should measure th voltage with the method I just described.

Ok, Some things I've come up with. The 220 line is closer to 240 and it is made up of two 120 lines. Also I'm not an expert at programming so I was thinking of rectifying the AC line and then using some kind of math in the software to calculate the AC value rather than trying to figure out that RMS ...

Hi there, To add to the previous ideas... The simplest circuit for measuring 220vac with an ADC with input range 0 to 5 volts i think is this: A single diode like 1N4007 in series with a 390k 0.25 watt resistor in series with a 10k, 0.25 watt resistor, with a 100uf, 10v electrolytic capacitor acros...

I am trying to find a good way to measure 220 AC with an ADC with a 5 volt range.
Thanks,