We're still measuring current or amperes, but it's direct and is measured differently from AC..again we have limitations...right.. because of the size wire to handle large amounts of current. The highest self contained DCA range is around 50 DCA...yep, varies from mfg to mfg but rule of thumb for us is 50. Anything above this is done with a "shunt rated meter". This will really get you confused, so hang on.
Just remember that in order to measure above 50 DCA an external shunt is required. Shunts are rated with a millivolt drop (yes millivolt...not milliamperes...trust me..). So if I were to measure 300 ADC the external shunt I would require would be a 300A/50mV shunt and yep the meter I would use would have a scale of 0-300 DCA and an input of 0-50 mVDC. Similar, just a little different...but you see how the meter and shunt are matched up...just as in all the other examples...just different devices...for what it's worth they also make a 100 mV rated shunt...and, yep, the meter we would use would have to rated or have an input of 100mV in this case...for below 50 ADC we can make "self-contained" meters that do not require an external device or shunt in this case...they range for say 20 microamperes (.00002 A) to 50 ADC. For these our input and scale are the same. There is a direct relationship of 1:1 for the input vs the scale of the meter...
