C. Identifying the Size of Copy Paper in the Cassette1. OutlineThe size of the copy paper inside the cassette is identified by the paper size sensormounted to the rear of the cassette holder.When the cassette is slid into the cassette holder, the paper size sensor is pushedby the boss on the cassette and turns on, thereby enabling identification of the width andthe length of the copy paper.The copier uses combinations of widths and lengths of copy paper to find out the sizeof the copy paper, and determines where to reverse the scanner and how to control theblanking exposure mechanism.The boss used to push the paper size sensor operates in conjunction with the guideplate inside the cassette, and its position is set when the guide plate is set to suit thecopy paper.2. Identifying the Size of Copy PaperThe copy paper length sensor consists of two photointerrupters, and the length isidentified with reference to combinations of the outputs of these two sensors.The paper width sensor, on the other hand, is a variable resistor, and the resistanceoutput of the sensor is used to identify the width of paper.Figure 5-206 shows the relationship between paper widths and variable resistoroutputs. You must register the correct basic settings whenever you have replaced theDC controller PCB or the sensor so that the relationship may be maintained. (SeeChapter 11 “Registering the Paper Width Basic Value.”)Figure 5-206A4/A3A4RSTMT-RSTMT-R(139.7mm) A4R(210mm) A4(297mm)Paper widthVariable resistor outputCOPYRIGHT © 1997 CANON INC. CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 5 PICK-UP/FEEDING SYSTEM5-8
