Re: Question on ADC
Yes, the most of multichannel ADCs consist of one ADC, one Sample/Hold (if any) and one multiplexer.
But there exist a real multichannel ADCs, for example ADS7861 from Texas Instruments, which has inside two ADC, each equipped with its own Sample/Hold and 2x1 multiplexer. So you can simulteneously sample two channels, for example V (voltage) and I (current) and then multiply two codes in microcontroller or PC and get a real instant power.
There is a similar chip of Analog Devices to (I do not remember the type).
Varuzhan