| CPC B41J 2/17506 (2013.01) | 14 Claims |
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1. A method of monitoring a fluid supply device, the device including a variable fluid volume to contain a supply of fluid and a variable gas volume to receive pressurized gas to pressurize the supply of fluid, the method comprising:
controlling a gas pressure of the pressurized gas to feed the fluid from the fluid volume, the gas pressure varying in a plurality of pressurization cycles;
monitoring a parameter of the pressurization cycles; and
determining a change in fill state of the fluid volume as a function of the monitored parameter,
wherein the parameter is a period of at least one of the pressurization cycles, and
wherein the determining the change in fill state comprises determining that the fill state is above an upper threshold level if a decrease in the period of the at least one of the pressurization cycles is detected.
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