I'm looking to eventually build an energy monitoring circuit using a raspberryPi as the controller and some type of ADC as the collector. I'm generally following the architecture of the emonTx used at openenergymonitor, except instead of using an Arduino I'm planning to use some type of smaller, discrete ADC, such as the Adafruit 1015 breakout board, or some variant of the MPC3208. While looking at various ADC options I've come across a few questions that I can't seem to find simple answers to...
1) How do I optimize input range vs. accuracy? The initial current-transformer I plan to use has a range of +/- 333mv, but it's possible to find similar ones that have an output range of +/- 1V. Is it correct to assume that the one with the "larger" range will give more precision? If so, is there a way to know where it's a meaningful amount of additional precision? (Practical question: do I need to go through the hassle/expense of finding/ordering a 1V model CT?)
2) The 1015 breakout board has a built in ability to increase the gain - but I have to assume that increasing the gain will also increase the noise. Is there any way to know (explicitly or just "by experience"?) whether the noise/inaccuracy introduced by the gain setting will be better or worse than the error introduced by building a more complicated circuit to lift the voltage into an acceptable range for the ADC?
3) Assuming I have control over the reference voltage on the ADC, is there a meaningful difference between using the bottom end of the range vs the top end of the range? Or does the convenience of being able to use an existing rail (i.e. the 5V that already powers the raspberryPi) outweigh this?
4) Is the extra circuitry on the breakout board useful in this type of application? I can clearly see where the ferrite and capacitor logic helps reduce the noise, but I have no idea whether we're talking about meaningful changes for this type of circuit. ;-)
And I fully recognize that it's possible that the answer is "it doesn't really matter, because no matter which of these you choose the circuit is going to be XXX accurate anyway which is way more precise than you need to monitor home energy use" - if that is indeed the answer then that info is useful, but I'd still like to understand how the above questions would be taken into consideration if we assume that ultimate precision is required (which I realize it's not...)