How should electric trailer brakes be tested for amperage draw?

Testing electric trailer brakes for amperage draw is correctly done using a DC ammeter in series with the brake circuit. This method allows for an accurate measurement of the current flowing through the brake system when it is activated. The ammeter is connected in such a way that it becomes part of the circuit, ensuring that the reading reflects the actual amperage being drawn by the brakes at that moment.

Using a standard multimeter, while it can measure DC current, typically requires some setup and might not provide the most reliable real-time reading when integrated into a circuit for this specific purpose. On the other hand, a resistance meter is designed to measure resistance and would not provide any information about current draw. Similarly, a voltage meter measures voltage and cannot directly measure amperage, making it unsuitable for this testing scenario. Thus, the most effective and accurate method for determining the amperage draw of electric trailer brakes is indeed the use of a DC ammeter in series with the brake circuit.