| 摘要 |
<p>PURPOSE:To stabilize the detection sensitivity for bulk material, by connecting a capacitor for high frequency bypass between a transistor of an oscillation circuit of a piezo-electric vibrator and a feedback electrode to prevent oscillation other than that at fundamental frequency. CONSTITUTION:A base of a transistor 7 for oscillation is connected to a feedback electrode 5 of a piezo-electric vibrator 1 through a resistance 8. A collector of the transistor 7 is earthed through resistances 9 and 10 connected in series while being connected to the electrode 5 of the piezo-electric vibrator 1 through a capacitor 11 for high frequency bypass. An electrode 4 for driving the piezo-electric vibrator 1 is connected to a connection point of the resistances 9 and 10 with a diaphragm 2 earthed. As the capacitor 11 is connected between the collector of the transistor 7 and the electrode of the piezo-electric vibrator 1, harmonic components of oscillation frequency due to variations in the part accuracy and the assembly of the piezo-electric vibrator 1 or the like are bypassed and the less frequently fed back to the base of the transistor 7. This suppresses undesired oscillating operation thereby enabling the detection of the presence of bulk material accurately.</p> |
