Patent attributes
The method of detecting a liquid amount includes applying a drive signal to a piezoelectric element provided at a predetermined position in a liquid containing section for containing a liquid, detecting an output signal from the piezoelectric element due to a residual vibration after the application of the drive signal, and detecting whether or not the liquid is present at the predetermined position based on the output signal utilizing difference in resonance frequency of the residual vibration depending on whether or not the liquid is present at the predetermined position. The drive signal includes a first drive waveform portion for driving the piezoelectric element at a resonance frequency of the residual vibration when the liquid is present at the predetermined position and a second drive waveform portion for driving the piezoelectric element at a resonance frequency of the residual vibration when the liquid is not present at the predetermined position.
