Patent ID: 7695083

Claim:
A printing apparatus to which a printing material container is detachably mounted, the printing material container having a piezoelectric element for detecting the amount of printing material stored in the printing material container and a memory unit storing frequency information on natural vibration frequency of the piezoelectric element, the printing apparatus comprising: means for acquiring the frequency information from the memory unit; means for generating a drive signal which has a first signal waveform at a first frequency and a second signal waveform at a second frequency which is different from the first frequency; means for selectively supplying either the first signal waveform or the second signal waveform to the piezoelectric element so as to increase the amplitude of the vibrations of the piezoelectric element; means for detecting a response signal outputted in response to vibration of the piezoelectric element; means for measuring the vibration frequency of the piezoelectric element contained in the response signal; and means for determining the amount of printing material stored in the printing material container based on the measured vibration frequency.