I need to measure current going through my PCB, which can be anything between -1200A to +1200A. Accuracy within 1-2% with bandwidth of anything higher than 50kHz.
The conductor is decided by now - I will use a copper bar.
The original plan was to use eight parallel 200uR resistors and measure the voltage drop across one of them. The problem is that bringing such current from the copper bar to several resistors seems to not be possible - the thin copper of the PCB might behave as a fuse.
Use several Hall effect sensors, arranged symmetrically round the bar, so that they add for the bar field, but cancel for external fields. Much the same principle as how a Rogowski Coil rejects external fields, but going down to DC as well.
Of course if you don't have the complexity of external fields, then only one is needed.
How about field sensors? If the busbar is rectangular it shouldn't be that difficult to place the sensor.
or other devices from Allegro https://www.allegromicro.com/en/products/sense/current-sensor-ics
Use a linear Hall effect sensor attached to or close to the bus bar. They are less than two dollars. However, they measure the magnetic field, so the output will vary due to external influences, although at 1000A the effect should be insignificant.
This is available as a flattened TO-92 package or a SOT-23. The device must be mounted such that the magnetic field passes through the flat surface orthagonally.
Super easy. Have a conductor of known characteristics somewhere in the system. This can (and arguably, should) be any conductor that has another job and is fit for the task. Having a dedicated ammeter shunt is unnecessary; any wire can be the "shunt" if its characteristics are known. And why wouldn't they be? :)
Measure the voltage difference between opposite ends of it.
simulate this circuit – Schematic created using CircuitLab
It is measuring down the voltage drop of the thick black line, because that line has known characteristics so it's a simple matter of plugging values into Ohm's Law.
It is vital that the voltage sense wire (fine black) have voltage drop on itself kept to functionally zero. That means the millivolt measurement device must itself be high impedance, and there cannot be ANY other load placed on these sense wires. You must resist the urge to use the sense wire as a supply wire for some auxiliary load.
Interesting note: Presuming that your supply is oriented with one leg of the source being nominally GND, the voltage seen by the voltmeter will be very close to 0 volts even though system voltage is hundreds of volts. However if the thick black wire suffers a casualty, all bets are off.
To measure currents as high as this, magnetic flux sensors are preferable to resistive, as they give you a galvanically isolated signal.
If you don't have galvanic isolation, you have to be extremely careful with the wiring, since a stray connection on the sensing circuitry can cause very high currents to flow, with considerable damage and the potential for injury.
Regardless of the measurement method, the big problem you will face with any self-made solution is calibration; it is all very fine making your own resistor, but the value will be very low and difficult to measure accurately; even with an (expensive) low-ohm meter, you will struggle to get within your 2% accuracy requirement.
Similarly, how are you going to calibrate the signal from a hall sensor? I'm guessing you don't have a calibrated source of 1000A to hand, in which case you'll have to use the highest calibrated current you can muster, and multiple turns of wire (e.g. 100 turns of 10A to make 1000A) and hope that the magnetic field isn't too distorted by the approximation.
When measuring DC railway traction current (up to 600A) we did use inline current shunts (somewhat hairy on a moving train) but ended up using LEM magnetic flux current-sensors which were much easier, and not too expensive, considering what they were measuring; I recently found one on an auction site for minimal cost, since there isn't much demand for them.
Use a shunt meant for busbar / screw mounting. There is really no point in bringing that amount of current back onto a PCB, if you don't need to.
We had an automotive application where we measured some quite extreme battery currents. We used something similar to this shunt, just packaged up and potted. For just 24,40 € this is shunt is practically free.
https://www.bourns.com/docs/product-datasheets/csm2f-7036-0.pdf
I would add a half decent current sense amplifier or an ADC with PGA on a small pcb and be done with it, something like this but a little bigger. This, you can then screw this module to the ends of a busbar. something like the bigger automotive fuses
