I didn't know much about Hall-effect sensors until I built a solar M&C system (in 2003) and I wanted to accurately measure currents (into/out of battery, out from solar array, and out of auxiliary charger). I didn't want to use shunt resistors because of losses, dealing with voltage offsets, and calibration uncertainty. I ended up using some metrology-grade Closed Loop Hall Effect Current Sensors (F.W. Bell CLN-200).
Hall-effect sensors by themselves are pretty poor for this application, but these sensors consist of a traditional (AC type) current transformer, but instead of a closed core, there's a Hall-effect sensor placed in a small gap in the core loop. Instead of measuring current from the transformer windings, the windings are fed from an op-amp current source with feedback from the Hall-effect sensor with the result that the magnetic field produced by the transformer windings exactly cancels the magnetic field produced from the current flowing through the source cable. The current in the cable is thus known because it equals the product of the CT current and the turns ratio (in this case 200/1).
The Hall-effect sensor here is only sensing the presence or absence of a magnetic field, and the CT is driven to null the field, so the system calibration is simple. (There's no need for any temperature compensation of the Hall-effect sensor.) Also, IIRC, these sensors have a pretty high operational bandwidth (DC to ~200kHz).
For a start, if you're monitoring your whole house, getting to zero load while keeping the sensor powered on is not trivial :)
For another, in my experience a lot of current sensing options are just a bit.... suspicious on the accuracy front. I've had resistive sensors tell me 1W is flowing through a plug with nothing plugged into it. Turning off a resistive load but the measurement slowing falling back to zero over several seconds, instead of dropping immediately. Solar monitoring current clamps that claimed zero current when the power company's meter said we were exporting 20W. Fancy £800 fluke clamp meters tell me 2A is flowing when there isn't even a cable in the clamp. Clamp ferrites getting broken in transit and producing bad results. Installers putting the CT clamp the wrong way. Installers installing the power meter the wrong way around, because the installation instructions assume you want to meter import not export.....
Current sensing is surprisingly hard to get right :)
i should preface this by saying that my knowledge here is entirely theoretical, and i'd be interested in knowing if i'm mistaken. as i understand the situation:
your ±1% 1Ω shunt resistor might actually be 0.99Ω, maybe depending on temperature (which changes after you power up the load), but you can get ±0.01% resistors pretty cheap these days
(maybe not if they have to handle 150 amps tho)
typically the bigger issue is the reference voltage the adc is comparing it against, because a voltage reference with 1% precision that's stable over time is pretty challenging, and also needs to be calibrated
but i'd think that would also be the case for calibrating the driver for the cancellation current in the hall-effect sensor?
since the device (clamp/fork meter) doesn't know if there is a current going or not... but if you control the load/current - it should be trivial to zero 'em.
Hall-effect sensors by themselves are pretty poor for this application, but these sensors consist of a traditional (AC type) current transformer, but instead of a closed core, there's a Hall-effect sensor placed in a small gap in the core loop. Instead of measuring current from the transformer windings, the windings are fed from an op-amp current source with feedback from the Hall-effect sensor with the result that the magnetic field produced by the transformer windings exactly cancels the magnetic field produced from the current flowing through the source cable. The current in the cable is thus known because it equals the product of the CT current and the turns ratio (in this case 200/1).
The Hall-effect sensor here is only sensing the presence or absence of a magnetic field, and the CT is driven to null the field, so the system calibration is simple. (There's no need for any temperature compensation of the Hall-effect sensor.) Also, IIRC, these sensors have a pretty high operational bandwidth (DC to ~200kHz).