Connect the positive power wire from the battery pack to the positive terminal on the light bulb socket. Strip the ends of each wire, twist them together and cover any exposed wire with a layer of electrical tape.
Connect the tip of the red positive probe from the multimeter to the negative terminal on the light bulb socket. Cover with a layer of electrical tape.
Connect the tip of the black negative probe from the multimeter to the negative wire on the battery pack.
Crack the glass light bulb using extreme care to prevent damage to the tungsten filament. Remove the glass bulb from the light bulb using a pair of pliers. Do not allow the filament to break or be touched by the glass.
Set the multimeter to measure DC current (amps) flow at the lowest setting.
Insert the light bulb into the socket without touching the exposed filament. Load the batteries into the battery pack. The light bulb filament should begin to glow lightly, as the battery pack is outputting 6 volts, and the bulb requires 12.
Read the screen on your digital multimeter. With current flowing through the filament at ambient room temperature and no wind, you should have a steady reading of current flow through the circuit. As air passes over the tungsten filament, it will be cooled, increasing the resistance and lowering the flow of current as read on the meter. To calibrate, place the bulb out of a car window and drive at a specific speed while taking readings of the current flow (in mA) on the multimeter.