DC Volt ranges that are most common are 50 mVDC (yep same 50 mVDC) as above to about 500 DCV. Similar to the ACV meters...contain too much voltage or potential in one spot, and it wants to beome a lighting bolt to the nearest conductor. So if you think of it as containing a large amoumt of voltage in one spot...say the size of a 3.5" barrel of a panel meter, the thing to do is spread it out so that some much of it isn't contained in a small area.
When measuring above 500 DCV an external resistor is used. This "speads" the voltage out so that so much isn't contained in one area. Common place is to use a meter that is 1000 Ohms per V or 1000 Ohms/V. This equates to a 1 mADC (.001 ADC) meter...(yep milliamps not millivolts...trust me...) without getting to involved in the math....the meter and external resistor are matched up...ok but just once...say we want to measure 1000V....so our ext resistor has to be 1000 Ohm per volt....that what the external resistor will be rate at so for a 1000 V our resistor is 1,000,000 Ohms or 1 meg Ohm and our meter will have a scale of 1000 DCV with an input of 1 mADC...and not to draw this out but the higher the voltage the smaller the rating of the meter you would want to use...differs from mfg to mfg...and just like all the rest the ranges below 500 DCV can be coinfigured as "self contained" meters.
