OP:
The meter you posted requires it to be placed in series with the load. It is rated at 10 amps. I would guess that a lot of the 12 volt DC loads could be in the range of 30-40 amps, which would burn out the meter.
This type of meter can have what is called a shunt. The meter would then be connected to the shunt to get a reading above 10 amps.
On a clamp on style amp meter the cable or wire being tested goes through the ring on top of the meter. It would then read the ampacity. Very easy to use.
Most clamp-ons have the same function as a multi-meter.
