We will present here more details of the electrical characteristics of q/m toner sensor on the basis of the technique developed in references [1] and [2].At first, toner particles are placed on the lower side of the parallel electrodes with piezoelectric element. Next, the piezoelectric element is driven by the rectangular pulse. Consequently, the dumped oscillation in the form of the sinusoidal waveform can be caused on the lower electrode. We can obtain some information for electrical states of the toner particles whether they can be lifted up from the center of the gap between two electrodes toward the upper one or not, from the first half period of the dumped oscillation waveform.By analyzing this waveform, we can obtain the value of charge-to-mass ratio (q/m) of toner particles.