Patent ID: 7614715

Claim:
A method of controlling a micro fluid ejection device having at least a middle zone with an associated middle zone heater and an edge zone with an associated edge zone heater, wherein the middle one is disposed relatively nearer a middle portion of a substrate for the micro fluid ejection device and the edge zone is disposed relatively nearer an edge portion of the substrate for the micro fluid ejection device, the method comprising: specifying a middle zone epsilon temperature, a middle zone target temperature, and a middle zone maximum temperature, sensing temperature in the middle zone to produce a middle zone temperature, applying a full middle zone power to the middle zone heater when the middle zone temperature is below the middle zone epsilon temperature, applying less than the full middle zone power to the middle zone heater when the middle zone temperature is both above the middle zone epsilon temperature and below the middle zone target temperature, wherein the middle zone power applied is calculated to achieve the middle zone target temperature, applying no power to the middle zone heater when the middle zone temperature is above the middle zone target temperature, specifying an edge zone epsilon temperature, an edge zone target temperature, and an edge zone maximum temperature, sensing temperature in the edge zone to produce an edge zone temperature, applying a full edge zone power to the edge zone heater when the edge zone temperature is below the edge zone epsilon temperature, applying less than the full edge zone power to the edge zone heater when the edge zone temperature is both above the edge zone epsilon temperature and below the edge zone target temperature, wherein the edge zone power applied is calculated to achieve the edge zone target temperature, applying no power to the edge zone heater when the edge zone temperature is above the edge zone maximum temperature, and when the edge zone temperature is both above the edge zone target temperature and below the edge zone maximum temperature, applying no power to the edge zone heater when the middle zone temperature is below the middle zone target temperature, and applying less than the full edge zone power to the edge zone heater when the middle zone temperature is both above the middle zone target temperature and below the middle zone maximum temperature, wherein the edge zone power applied is calculated to achieve the middle zone temperature.