Discussion about the measurement accuracy of the densitometers

Transmission-type black-and-white densitometer is widely applied by the industry of graphic arts, film strip developing and printing, labor protection, photosensitive film, medical and health work and etc. Therefore, the measuring accuracy results of densitometer have directly influences on the quality of production and result analysis. For making sure of measuring accuracy in transmission-type black-and-white densitometer, densitometer measuring and verification is very important. Currently many companies are using their own classification group optical density disk to measure their instruments. In other words, they send optical density disks attached the instrument to the measuring unit for verification (calibration) and then use the optical density disks to calibrate their instruments. Is this method feasible or not? Can it make sure of the measuring result accuracy in transmission-type black- and-white densitometer? Can it replace the method that measuring unit uses the standard optical density disks to periodically verificate (calibrate) their densitometers? Moreover, customs often argue that when they used the instrument which is indicated as failure measuring result by measuring unit to verificate their own optical density disks attached the instrument, the measuring result is passed. That means the result of using their own classification group optical density disk to measure their instruments sometimes may be different from the result of using measuring unit´s standard optical density disk.