| 摘要 |
<p>A liquid sensor system particularly suitable for commercial washing machines for drinking glasses and soft drink dispensers employs a capacitive detector providing a tortuous path through which the liquid passes and constituting part of the dielectric of the resultant capacitor. The pumps supplying the liquid through the capacitor to the dispensing means are controlled in accordance with the capacitance, as measured by a circuit. A preferred measuring circuit comprises a pulse generator; one series of pulses split from the generator output is delayed by a fixed period and fed to a flip-flop, while the second series also from the generator output are delayed by a period dependent upon the sensor capacitance and are also fed to the flip-flop, the output of which is dependent upon which series of pulses is in advance of the other. The circuit also provides for automatic adjustment of its sensitivity upon start-up or reset to adjust for differences in the sensors and the liquids.</p> |
