Most multimeters can only measure current up to 10 A maximum. The current measuring facility is intended only for small current components and, in particular, for electronic circuits.
The instrument will almost certainly be damaged if it is used to measure the current to motors and other power circuits.
The basic current range can be extended by using external shunts (DC) and current transformers (AC).
These accessories are generally purchased separately from the instrument manufacturers.
The procedure to be used to measure current in a small current circuit is:
PROVE the correct instrument operation.
SWITCH the instrument to the highest current range (either acA or dcA as appropriate).
TURN OFF the power to the circuit to be tested and discharge all capacitors.
OPEN the circuit in which current is to be measured – removing a fuse-link often gives a convenient point for current measurement.
ADJUST the test leads as designated for current measurement.
Securely connect the probes in series with the load in which current is to be measured.
Turn ON the power to the circuit being tested.
Note the current size on the meter display.
Turn OFF the power to the circuit being tested and discharge all capacitors.
Disconnect the test probes and switch the instrument to OFF.
Reconnect the circuit that was being tested.
Often, the most convenient way to measure current is to use a clampmeter, which is simply clamped around an insulated conductor.