I would recommend you use one of these true RMS current transducers with 0-5 Vdc output, they have a basic accuracy of 0.5%. **broken link removed**
You can get these transducers with current ranges from 0-0.5A, 0-5A, 0-10A and so on. So it should be possible to find a transducer with the right current range for your purpose. If you choose one with 0-5Vdc output you can connect it directly to your ADC. It doesn't get easier than this.
You can also find true RMS AC voltage tansducers, AC power transducers and frecuency transducers at this site as well.
Data sheet for true RMS AC current transducers: **broken link removed**
Data sheet for AC current transducers:
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Application note for AC current transducers:
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