| 摘要 |
PURPOSE: To accurately judge validity of a drive status signal by causing a monitor to evaluate, in regard to the vibration of a vibrating body, whether the output characteristic value of a frequency signal from an energy converting element for monitoring which generates a frequency signal belongs to the predetermined characteristic value range or not. CONSTITUTION: Polarized two groups of piezoelectric elements are arranged on the surface of a stator 1, drive electrodes 1-1 and 1-2 are provided on the piezoelectric elements of each group to apply the frequency signals having the phases with difference of 90 degrees and a monitor electrode 1-3 for detecting the vibrating condition of the stator is arranged on the piezoelectric element electrically insulated from the drive electrodes 1-1, 1-2. The periods of high level and low level of the signal from the monitor electrode 1-3 converted to the logic level are measured. When this period is within the predetermined range, a delayed phase angle of the signal of the monitor electrode 1-3 for the drive electrode 1-1 is monitored so that the drive frequency is never shifted to the side lower than the resonance frequency. |
