When an ammeter is placed in series with a circuit, it ideally drops no voltage as current goes through it. In other words, it acts very much like a piece of wire, with very little resistance from one test probe to the other.

How does an ammeter work?

Ammeters work to measure electrical current by measuring the current through a set of coils with a very low resistance and inductive reactance. ... If the ammeter were connected in parallel, the path may become short-circuited such that all the current will flow through the ammeter instead of the circuit.

How do I know if an ammeter is working?

Test the internal fuse of your ammeter.

If the resistance rating is low, your fuse is good. The resistance reading of your ammeter will be indicated on a display on the front of the meter. You may have to adjust the power range before it can read the low level of a working fuse.