Patent ID: 8246132

Claim:
An image forming system, comprising: a fluid ejector unit configured to eject drops of fluid; a replaceable fluid supply unit configured to supply fluid to the fluid ejector unit; an out of fluid detection unit configured to detect an out of fluid state of the replaceable fluid supply unit; a drop counter unit configured to determine a total drop count by counting a total number of drops ejected from the fluid ejector unit in response to the detected out of fluid state; and a correction factor determination module configured to determine a correction factor including at least a volume ratio parameter of the replaceable fluid supply unit to be used to determine an amount of remaining fluid of a subsequently-installed replaceable fluid supply unit such that the volume ratio parameter corresponds to a ratio of a nominal fluid volume and an estimated fluid volume of the replaceable fluid supply unit and the estimated fluid volume is determined based on at least the determined total drop count the subsequently-installed replaceable fluid supply unit is configured to replace the replaceable fluid supply unit in response to the detected out of fluid state, the correction factor is determined according to the following (CF) equation CF=(1+FLUID_VOLnom/FLUID_VOLest)/2, and the estimated fluid volume of the replaceable fluid supply unit is determined according to the following (FLUID_VOLest) equation FLUID_VOLest=(TL_NOdrops)×(DW)/FD; and wherein: FLUID_VOLest is the estimated fluid volume corresponding to the replaceable fluid supply unit; TL_NOdrops is the total drop count corresponding to the total number of drops ejected from the fluid ejector unit by the fluid supplied by the replaceable fluid supply unit: DW is a drop weight associated with the fluid ejector unit; and FD is a fluid density corresponding to the fluid of the replaceable fluid supply unit; and wherein: CF is the correction factor corresponding to the replaceable fluid supply unit; FLUID_VOLnom is the nominal fluid volume corresponding to the replaceable fluid supply unit; and FLUID_VOLest is the estimated fluid volume corresponding to the replaceable fluid supply unit.