As the internal resistance (or input impedance) of a multimeter influences the circuit you are measuring, and therefore influences the reliability of you measurement, it would make sense to me to if this internal resistance were mentioned somewhere in the multimeter spec sheet.
For example, when measuring DC current through a low resistance load, a couple of Ohms internal resistance can make a big difference, so it would be helpful to know at least its order of magnitude.
However, although some manufacturers (e.g. Fluke) specify the input impedance for voltage measurements, I have not been able to find similar specifications for the current measurement part (e.g. the ammeter internal resistance or shunt resistor values for different measurement ranges).
I know how to measure the ammeter resistance using a load in series and resistors (or decade box) in parallel with the multimeter, but I don't understand why manufacturers do not provide these values in their spec sheets.
Does anyone know? Am I missing something obvious? Am I looking at the wrong specification perhaps?