Use a multimeter set to current mode
Break the circuit and connect the meter in series
Select the correct current range
Start with the highest range if the current is unknown
Connect the red probe to the current input jack
Connect the black probe to the common jack
Read the displayed current value
Use a clamp meter around one conductor for AC current
Apply Ohm’s law if voltage and resistance are known: I = V / R
Measure the voltage across a known resistor and divide by its resistance
Ensure the meter rating is not exceeded
Turn off power before changing meter connections
Verify whether the current is AC or DC
Check the circuit diagram for the correct measurement point