| 摘要 |
An arrangement for indication of the need to clean a filter, e.g. in a stove hood, has a time circuit actuated by a push button during at least 0,5 second, whereby a capacitor is charged. After the push button has returned to rest a discharging of the capacitor takes place during some 4-5 minutes, simultaneously an E-cell is charged by some 1 mA. When the discharging of the capacitor is finished the E-cell is connected in a circuit with an opposite current direction and an amperage, which is proportional to the current of the ventilator motor, and a signal lamp is put out. When the ventilator motor is not in duty, nothing is going on in the E-cell, as no current passes. A condition for making the cell work is that the voltage on it exceeds a step of some 1 V. This is the voltage step which can be used just for the reason that no reduction of time to the next cleaning shall take place when the motor works at minimum rpm. When finally the E-cell is discharged a signal lamp indicates <<clean the filter>>. |
