Head unit and liquid ejection apparatus

A liquid ejection apparatus comprising:

• a drive circuit configured to output a drive signal;
• a first pressure chamber a volume of which varies in accordance with the drive signal;
• a second pressure chamber a volume of which varies in accordance with the drive signal;
• a first nozzle that communicates with the first pressure chamber and the second pressure chamber, and that is configured to eject a liquid;
• a first piezoelectric element configured to output a first residual vibration signal according to a first residual vibration generated in accordance with a volume change of the first pressure chamber;
• a second piezoelectric element configured to output a second residual vibration signal according to a second residual vibration generated in accordance with a volume change of the second pressure chamber;
• an inspection signal output circuit to which the first residual vibration signal and the second residual vibration signal are input, and which is configured to output an inspection signal;
• a processor configured to determine an ejection state of the liquid from the first nozzle based on the inspection signal;
• a first switching circuit configured to switch whether to output the first residual vibration signal and the second residual vibration signal to the inspection signal output circuit;
• and
• a conveyance mechanism configured to convey a medium on which the liquid ejected from the first nozzle lands, wherein
• the first piezoelectric element and the second piezoelectric element are electrically coupled at a first node, and
• the first switching circuit is configured to switch a conduction state between the first node and the inspection signal output circuit.