Inkjet printing system, fluid ejection system, and method thereof

An inkjet printhead system comprising:

• a number of inkjet printhead devices, an inkjet printhead device comprising:
• a fluid supply chamber to store fluid;
• a plurality of ejection chambers including nozzles and corresponding ejection members to selectively eject the fluid through the respective nozzles, wherein at least one of the ejection chambers is a test chamber;
• a channel to establish fluid communication between the fluid supply chamber and the plurality of ejection chambers;
• an air bubble detect micro-electro-mechanical systems (ABD MEMS) pressure sensor having a sensor plate disposed in the test chamber to output a voltage value corresponding to a cross-sectional area of an amount of fluid in the test chamber;
• and
• a converter module to output a count value corresponding to the respective voltage value output by the ABD MEMS pressure sensor;
• and
• a count determination module to:
• determine a supply condition based on the count value output by the converter module and the amount of time to refill the at least one ejection chamber;
• and
• determine that the fluid supply chamber is in a pre-exhaustion condition when back pressure and refill time increase.

A method of determining a supply condition of a fluid ejection system, the method comprising:

• establishing fluid communication between an ejection chamber having a nozzle corresponding thereto and a fluid supply chamber of a fluid ejection device by a channel;
• outputting voltage values by a micro-electro-mechanical system (MEMS) pressure sensor unit corresponding to at least respective amounts of fluid in the ejection chamber;
• outputting count values by a converter module corresponding to the voltage values output by the pressure sensor unit, the count values indicative of supply conditions;
• outputting values indicating an amount of time to refill the at least one ejection chamber;
• determining a supply condition by a count determination module based on a count value output by the converter module and a value indicating an amount of time to refill the at least one ejection chamber;
• and
• determining that the fluid supply chamber is in a pre-exhaustion condition when back pressure and refill time increase.