| 摘要 |
PURPOSE:To clearly detect the existence of an ink by electrically excite an electroacoustic transducer element installed inside an ink tank, etc. and detecting a change of the dynamic impedance of load. CONSTITUTION:The damping admittance of a vibrator is Yd, and the dymanic admittance Ym. Then a sufficiently high circuit constant P is selected. The output voltage Eo of bridge circuit represents a value proportional to vibration speed v according to a publicly known formula. If power supply voltage E1 is now kept constant, it is possible to detect a change the acoustic impedance of load pased on a change of output voltage Eo. Thus it can be distinguished whether a liquid or air is touching a vibration plate. Consequently, the faulty case such as seen in the past does not occur that the existence of ink can hardly be determined due to the fouling of a transparent window. |
