yes, probably - but caution that some meters terminate the test current, (certainly on the higher ranges) if the supply is not disconnected  within a short time to avoid danger - which may not give time for the ammeter under test  to finish its cycle of Analog to digital conversion.

If your RCD tester is one of those then it may be easier to have some known load of known resistance and some known voltage, once upon a time I'd have said a 60W light bulb is ~ 1/4A when hot, but nowadays filament lamps are the rarity, and low current resistive loads are rare and inductive things like motors and transformers are messy because the current and voltage are not in step so the wattage and the current are not simply related by I=P/V.

Equally mains rated resistors are quite cheap.  10k wirewound will give 23ma at 230V, for example. (but get very hot dissipating 5 watts for more than a couple of minutes at a time)   A few in series / parallel combinations in a suitable enclosure can make a home calibration rig. (Resist any temptation to consider choc bloc screwed to a bit of old floorboard as a permanent assembly.)

Or a cheap multimeter with an amps range that is rather less bashed around than the working one..

yes, probably - but caution that some meters terminate the test current, (certainly on the higher ranges) if the supply is not disconnected  within a short time to avoid danger - which may not give time for the ammeter under test  to finish its cycle of Analog to digital conversion.

If your RCD tester is one of those then it may be easier to have some known load of known resistance and some known voltage, once upon a time I'd have said a 60W light bulb is ~ 1/4A when hot, but nowadays filament lamps are the rarity, and low current resistive loads are rare and inductive things like motors and transformers are messy because the current and voltage are not in step so the wattage and the current are not simply related by I=P/V.

Equally mains rated resistors are quite cheap.  10k wirewound will give 23ma at 230V, for example. (but get very hot dissipating 5 watts for more than a couple of minutes at a time)   A few in series / parallel combinations in a suitable enclosure can make a home calibration rig. (Resist any temptation to consider choc bloc screwed to a bit of old floorboard as a permanent assembly.)

Or a cheap multimeter with an amps range that is rather less bashed around than the working one..