Hi,
I woke up with a clear explanation.
ModemHead, you are right. That is the correct explanation.
Burden Voltage, is nothing more than Voltage and its the same as the
Voltage Drop caused
by the internal resistance of the multimeter. Volts. Now mV/mA is another way to talk about
the internal resistance of the multimeter. mV/mA does
NOT represent burden voltage,
but is a measure of its cause.
Burden Voltage is not a constant while mV/mA is a constant. (more or less) Well, not exactly a
constant because the multimeter's internal resistance changes between current scales and
some times between voltage levels as in the UT61E. (not sure about the last one though).
The bottom line is that the thing that characterises a multimeter's accuracy in measuring low
currents is not the burden voltage but its internal resistance. That is what has to been listed
in its performance specifications. Especially in multi-meters sold for electronics.