Printer fluid impedance sensing in a printhead

A printhead controller comprising:

• a processing resource;
• and
• a memory resource storing machine readable instructions to cause the processing resource to:
• receive impedance sensor values from an impedance sensor in a printhead;
• and
• determine whether the received impedance sensor values correlate to the production of an effective drive bubble for the printhead.

A system comprising:

• a printhead including:
• a firing chamber to receive printer fluid;
• a nozzle in fluid communication with the firing chamber, wherein the nozzle is to direct printer fluid droplets ejected from the printhead;
• and
• an impedance sensor positioned in the firing chamber to contact printer fluid to measure impedance values of the printer fluid;
• and
• a printhead controller in data communication with the impedance sensor, the printhead controller including:
• a memory resource storing machine readable instructions to cause a processing resource to:
• receive impedance sensor values from the impedance sensor;
• and
• determine whether the received impedance sensor values correlate to the production of an effective drive bubble for the printhead.