Service manual

MDS E-SCAN MPR E-SCAN INFORMATION
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4.1.1.2 CCD Linear Array
The linear array used in the E-Scan includes 2048 individual photo sites. Each of these photo-
diodes independently measures the incident radiation between scan intervals and stores an
electrical charge, which reflects the measured intensity. At the end of this interval the shift gate
is activated and the charges are simultaneously transferred into the shift register. The charges are
transferred out of the shift register in "bucket brigade" fashion through the signal output buffer.
The output is an analog voltage representative of the charge per pixel (photo site) and is
reset to ground between each transfer.
4.1.1.3 Signal
CCD Signal
To further increase resolution the signal is rectified and averaged as shown in the following
figure. This signal is used to control the LED current to eliminate the effects of process color
changes, suspended solids, entrained air and other problems associated with non scanning
refractometers. The refractive index information is also contained in this signal in the form of
the ratio of A to B.