On Sat, 18 Sep 2004 22:20:36 -0700, "Bob Headrick" <bobh_at_proaxis.com>
wrote:
> HP printers that calculate ink usage typically count drops and may
> also apply correction factors based on storage time, temperature
> or other factors.
See HP's US patent 6,431,673 at
http://www.uspto.gov/patft/index.html
the excerpt of which states:
United States Patent 6,431,673
Heim , et al. August 13, 2002
Ink level gauging in inkjet printing
Abstract
The gauging method generally follows a drop count approach to ink
level gauging while making more precise the relationship between the
expelled-drop count and the weight of ink actually expelled, thereby
to provide more accurate ink level gauging. The printhead temperature
is monitored as each swath of an image is printed. Moreover,
temperature variations that occur within each swath are noted so that
the corresponding intra-swath variations in drop weight are factored
into the calculation of a net ink drop weight that more closely
approximates the drop weight actually ejected. The method also
factors in the effect that printing frequency has on drop weight.
Inventors: Heim; Rory A. (Corvallis, OR);
Castle; Steven T. (Philomath, OR)
Assignee: Hewlett-Packard Company (Palo Alto, CA)
