One can measure the amperage any place along the welding leads using a tong type ammeter. Make sure the ammeter can read the type of current being measured, i.e., direct current or alternating current.
If the amperage expected is less than half the range of the ammeter, one can pass the same lead through the tongs twice. That will double the reading to provide a more accurate reading. Ideally, the amperage should be about half the amperage range of the ammeter.
Best regards - Al