| 摘要 |
PROBLEM TO BE SOLVED: To prevent effect of disturbance of a cell signal accompanying the stoppage of downward action of a probe by providing dead time during a specified period from the generation of information using contact information when the probe comes into contact with a liquid surface to be detected. SOLUTION: A small change happens in the electrostatic capacitance by vibration and the electrostatic capacitance falls below a voltage value VTH while a probe is stopped detecting a liquid surface. At this time, an output TP7 of a second comparator circuit 36 of a signal comparator circuit changes HIGH from LOW. In an F/F circuit 34, when a setting signal of a TP5 is active, a higher reference of the setting signal allows the output Q thereof to keep the LOW level even when a clock is inputted so that malfunctioning by vibration during the stoppage can be avoided. In other words, while a sensor probe is in contact with the liquid surface, malfunctioning is prevented by keeping a liquid level detection signal 19 inverted. When the probe rises, a sensor signal becomes smaller sharply down below the voltage value VTH. The output TP7 of the circuit 36 is inverted to HIGH from LOW to reset the circuit 34. |
