Fluid ejection device combining drive bubble detect and thermal response

A fluid ejection system comprising:

• a fluid ejection device including:
• a plurality of fluid chambers, each fluid chamber including:
• a vaporization chamber;
• a thermal drive bubble formation mechanism to vaporize a portion of a fluid in the vaporization chamber to form a drive bubble during a firing operation;
• a drive bubble sense element separate from the thermal drive bubble formation mechanism and in contact with the fluid;
• and
• a thermal sense element;
• and
• a sense controller to:
• inject a fixed current through the vaporization chamber via the drive bubble sense element of a selected fluid chamber during a firing operation to generate a first voltage signal representing a voltage response of the vaporization chamber and indicative of the formation of a drive bubble;
• inject a fixed current through the thermal sense element of the selected fluid chamber to generate a second voltage signal indicative of a thermal response of the vaporization chamber during the firing operation;
• and
• a fluid chamber monitor to determine an operating condition of the selected fluid chamber based on the voltage response and the thermal response of the vaporization chamber combined.

A method of operating a fluid ejection device comprising:

• energizing a thermal drive bubble formation mechanism to vaporize a portion of a fluid in a vaporization chamber of a fluid chamber to form a drive bubble during a firing operation of the fluid chamber;
• injecting a current through the vaporization chamber during the firing operation to generate a voltage signal representing a voltage response of the vaporization chamber;
• measuring a thermal response of the vaporization chamber during the firing operation;
• and
• determining an operating condition of the fluid chamber based on the voltage response and the thermal response of the vaporization chamber.