Kodak DryView 8300 Service Manual page 242

SERVICE MANUAL
THEORY
The DENSITOMETER ASSEMBLY has an incandescent LAMP with a green FILTER and a photo-detector
SENSOR. Current is passed through the LAMP, causing it to illuminate. When the current is increased, the
LAMP becomes brighter. Its output is measured by the photo-detector SENSOR and sent to a pair of A/D
converters on the CPU BOARD, which monitors and records the digital values at 3 stages. The A/D
converter circuits have a low gain amplifier, used for the above density measurements, and a high gain
amplifier that is more accurate for D-min measurements. The resulting measurements are indicated by the
DL and DH digital values available during debug monitoring. If the digital values are within an expected
range, the actual values are recorded as reference points when no film is present.
When a calibration film is moved through the DENSITOMETER, new values are recorded for the 20 bands
of gray levels on the sheet. Each scan line of each band is measured to check that the middle of each
band is used for value calibration. The digital value output for each amplifier is displayed for each scan line
when monitored with the debug program. These values are compared to the reference values to determine
the density of the bands.
1908110 2004 December Rev. S
7-74