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 material stored in the container and a memory unit storing the 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 having a first signal waveform at a first frequency and a second signal waveform at a second frequency different from the first frequency, means for selectively supplying either the first or 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, means for measuring the vibration frequency contained in the response signal, and means for determining the amount of material stored in the printing material container based on the measured vibration frequency.