How would you measure voltage passing through a light bulb using a digital multimeter?
Simply set the multi meter on DC voltage, which is denoted by a
line with dotted lines under it. Then place the red lead on the
positive side of the bulb and the black lead on the negative side.
If you do this incorrectly it will be a negative number but the
same number if the leads are reversed.
If you have a bad bulb the meter will show all zero´s. Otherwise
you´ll get something like 0.01 which is a good indicator for a
working bulb.
The voltage across the light bulb will be the same voltage as
the supply. Regardless of whether the bulb is good or bad the
voltage potential will still be there. You are measuring voltage
not amperage.