Electrophotography – Diagnostics – Document handling
Patent
1999-07-06
2000-12-05
Brase, Sandra
Electrophotography
Diagnostics
Document handling
G03G 1500
Patent
active
06157791&
ABSTRACT:
An embodiment of a media quantity sensing device and a media type sensing device includes a first, a second a third, and a fourth electrode. The first electrode is positioned above a media tray and the second electrode is positioned on the media tray below the media. The third and the fourth electrodes are positioned so that the media leaving the media tray passes between them. The media quantity sensing device further includes a measuring circuit coupled to a controller. The measuring circuit includes a first dual slope integrator to generate a first square wave output signal having a frequency dependent upon the dielectric constant of the media between the first electrode and the second electrode. The measuring circuit further includes a second dual slope integrator to generate a second square wave output signal having a frequency dependent upon the dielectric constant of the media between the third electrode and the fourth electrode. The measuring circuit also includes a frequency measurement unit to measure the frequencies of the first and the second square wave output signals. The controller reads the frequencies from the first and the second square wave output signals. The controller determines the media type in the media tray based upon the frequency of the first square wave output signal. Based upon the media type information, the controller selects and accesses a lookup table to determine the quantity of the media in the media tray by comparing the frequency of the second square wave output signal to values in the lookup table.
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Haines Robert E.
Phillips Quintin T.
Weaver Jeffrey S.
Brase Sandra
Hewlett--Packard Company
Wisdom Gregg W.
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