Marc:

AC and DC clamp on ammeters use entirely different electrical mechanisms. AC
meters measure the current induced from the wire to the surrounding clamp on
coil. DC meters use a physics principle called the Hall Effect. Some meters
like mine use both.

I have a AC/DC clamp on ammeter sold by Ancor (but probably made by Fluke).
It measures AC and DC current in two ranges: 0-200 amps and 0-40 amps. The
lower range is good for a tenth of an amp real world resolution.

Since we mostly live in a DC world, this meter is the best troubleshooting
device a boater can have. I paid about $200 for mine and couldn't live
without it.

David