This application note describes the techniques that can be used to compensate for the natural variation in output intensity of miniature fluorescent bulbs. The output intensity for any 20nm bandwidth can vary by as much as +50% from device to device. A similar figure to LED output intensity tolerance. The major factors, which cause this variation, are differences in the phosphor coating from device to device and tolerances of the anode and cathode geometries. External influences such as ambient temperature will affect the output intensity. Before discussing correction schemes the typical distribution of output intensities is shown for a long wavelength ultra-violet miniature fluorescent device. Similar distributions are obtained for other spectral devices. The output intensities at 366nm of 50 lamps were measured. The distribution is shown below.