HP 2500C Series User Manual download pdf (Page 136)

Functional Overview6-16

Paper Paths and Components

Linefeed Accuracy

A closed loop drive system was used to ensure good positional accuracy of the

transmission system. This involved the use of a rotary encoder disc mounted on the drive

roller shaft in conjunction with a three gears gear-train design. The mounting of the

encoder disc directly on the drive shaft helps to eliminate gear and motor errors and at the

same time offer direct feedback on the position of the drive roller shaft. However, errors

due to encoder disc eccentricity, drive roller run-out and media-roller interface will still

be present.

The encoder disc is a rotary disc made from Kodak LPF7 film. A total of 1440 counts

were printed on the disc at an optical diameter of 58.2125 mm. The count to count

spacing is 200 LPI. This spacing translate into a linear movement of 1/300 inch on the

circumference of the ∅38.808 mm drive roller.

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HP 2500C Series User Manual Page 136