I think we determined in this thread that when measuring a channel, the IotaWatt definitely doesn’t lack bandwidth, at least while it’s looking at that channel. It goes almost all the way out to an extraordinary 20KHz. The downside is it only looks at every 25th cycle of each channel.
If you don’t have enough ADC horsepower for the job at hand you have to make compromises. Here the design choice is whether to reduce the per-channel sampling rate (and hence the bandwidth) Vs skipping cycles altogether. I would have gone with the former (especially with the bandwidth currently sitting out at ~20KHz), IotaWatt went the latter… but each to their own.
If you don’t want to be conflicted by that compromise at all, consider something like this. From the moment it first syncs to zero crossing, it measures every cycle of every channel forever, no exceptions. That’s 15 I and 3 V channels at 8,376 (V,I) sample pairs per second per channel and it’s not even breaking into a sweat. That’s actually pretty close to the rates my energy IC based monitor runs at. It does all it’s work at 8000 sample pairs per second per channel (albeit 24-bit samples instead of 12-bit) and even then, only claims 2KHz bandwidth. I guess they’re leaving themselves plenty of headroom there.