Guide to UV Measurement
Lamps: Power
UV lamps usually consist of a tubular shaped bulb, and it is common to describe their operating power in “watts per inch.” This is derived simply from the electrical power input divided by the effective length of the bulb. It does not have a direct meaning to the output efficiency of a lamp system, to the spectral conversion efficiency, to the curing performance, nor to the UV irradiance delivered to a work surface.
For arc lamps, input “watts per inch” is the product of the electrode tip-to-tip rms voltage and phase-corrected current, divided by the tip-to-tip distance. For microwave powered lamps, input “watts per inch” is the total microwave power in the bulb cavity divided by the end-to-end reflector inside distance. So, while not an indicator of performance, input “watts per inch” is typically used to describe the general class of UV lamp system.