Fluid level detection apparatus and method for determining the volume of fluid in a container

A fluid level detection system (110, 200, 300) for determining the volume of fluid in a container (60. 62, 112, 202, 302, 338, 380, 396, 406, 428) is disclosed. An embodiment includes a fluid container (60, 62, 112, 202, 302, 338, 380, 396, 406, 428), a reference chamber (124, 212), a pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426), an air source (128, 216, 314), an air management system (126, 214, 312) including at least one orifice (154), a pressure sensor (158, 238, 326), a time measurement device (160, 240, 328), and a computing device (160, 240, 328). The air management system (126, 214, 312) selectively pressurizes the reference chamber (124, 212) or pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426) and selectively discharges the reference chamber (124, 212) or pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426) via the orifice (154). The time measurement device (160, 240, 328) determines elapsed time ( DELTA tR) for pressure in the reference chamber (124, 212) to drop from pressure (PR1) to pressure (PR2) and elapsed time (Atp) for pressure in the pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426) to drop from pressure (PP1) to pressure (PP2). The computing device (160, 240, 328) determines a volume of air in the pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426) based upon the reference chamber (124, 212) volume, elapsed time ( DELTA tR), elapsed time (Atp), and pressures (PR1), (PR2), (PP1), and (PP2), and determines the volume of fluid in the container (60, 62, 112, 202, 302, 338, 380, 396, 406, 428) based upon the pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426) volume and the volume of air in the pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426). A printing device (20) incorporating an embodiment of the fluid level detection system (110, 200, 300) is also disclosed, as is a method (350) for determining the volume of fluid in a container based upon the volume of air in a pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426). An apparatus for use in a printing device is disclosed that includes a printing composition container (60, 62, 112, 202, 302, 338, 380, 396, 406, 428), a printing composition port (122, 205, 305, 391, 419, 433) coupled to the container (60, 62, 112, 202, 302, 338, 380, 396, 406, 428), a pressure chamber (114, 204, 304, 376, 394, 404 and 407, 426) around the container (60, 62, 112, 202, 302, 338, 380, 396, 406, 428), and an air port (143, 243,