Shunt resistors for DMM6500

[drummerdimitri]

So I'd like to make some power measurements using the power script that has been written for the Keithley DMM6500 DMM using the DCV ratio.

I would like to measure anything from small led's to power electronics drawing thousand + amp peaks (DC battery tab welder).

Not sure if all shunts are built the same or if the ones I can get off of Aliexpress are good enough that go for a few bucks each.

Will want to make the most accurate measurments possible so what range of shunts should I get?

Also, if a Shunt is rated at 500A does that mean such a rating should no be exceeded or is it just to indicate that at that current level the burden voltage will be 75 mV?

[Kleinstein]

The rated current is usually the maximum current (it's different for very small currents). For short spikes below the thermal time constant (e.g. some 1-30 seconds, depending on size) the current can be higher.  For best accuracy it may not even be a good idea to use the full rated current, as heating can add quite some error. This can especially be a problem with the cheap ones with high TC and poor cooling / exaggerated rating.