Fluid supply control

A fluid ejection system comprising:

• a fluid supply reservoir to store fluid;
• a fluid ejection die comprising a plurality of nozzles to eject fluid, the fluid ejection die further comprising at least one temperature sensor disposed thereon to sense a temperature of the fluid ejection die;
• a fluid supply subsystem that fluidly connects the fluid supply reservoir and the fluid ejection die, the fluid supply subsystem comprising at least one valve to regulate conveyance of fluid from the fluid supply reservoir to the fluid ejection die;
• and
• a control engine to determine a temperature change for the fluid ejection die corresponding to at least one ejection event, and to adjust the at least one valve based at least in part on the temperature change for the fluid ejection die corresponding to the at least one ejection event to thereby regulate conveyance of fluid from the fluid supply reservoir to the fluid ejection die based at least in part on the temperature change of the fluid ejection die;
• wherein the control engine is further to:
• control the fluid ejection die to eject fluid drops for a set of ejection events;
• determine a temperature change of the fluid ejection die associated with the set of ejection events;
• determine a back pressure associated with the fluid supply subsystem based at least in part on the temperature change of the fluid ejection die associated with the set of ejection events;
• and
• adjust the at least one valve based at least in part on the backpressure associated with the fluid supply subsystem.