Amps aren't measured the way that voltage is, a critical difference. Last month, we discussed how voltage is measured in parallel; for instance, when a multimeter's positive and negative test leads are placed on the positive and negative terminals of a battery. Conversely, amperage is measured in series. When any electrical component is placed in series—be it a multimeter, a light, or a battery—it's essentially inserted into a circuit rather than alongside it or in parallel. For measurement purposes, this means that up to about 10 amps, the multimeter becomes part of the circuit as a current-carrying conductor. For example, if you wanted to determine how much current an anchor light used, you'd separate one of the light's conductors at the base of the mast or the electrical panel. Setting your meter to AMPS DC, you'd then attach one lead (it doesn't matter which) to the wire leading to the light and the other to the energized conductor that ultimately travels to the source of power, the battery. (These two conductors are referred to respectively as the "load" and the "line.") When power is applied, the light is illuminated, and the meter will simultaneously indicate how many amps are being drawn. A 12-volt, 20-watt light should draw about 1.5 amps. If, however, it's drawing 8 amps, you might conclude that the insulation on the positive wire leading up the mast conduit (all mast wiring should be in a conduit) has chafed and is creating a "pseudo" short circuit. This will unnecessarily consume battery power, and it may also accelerate mast corrosion.