| 摘要 |
A measuring part 67 measures the potential of a collecting electrode 66 having collected positive and negative ions respectively generated by ion generating parts 61 of ion generators 6a and 6b and ion generating parts 62 of ion generators 6c and 6d. In the judgment of the presence or absence of ions, the ion generators 6a and 6b and the ion generators 6c and 6d are alternately turned ON/OFF. In ion judgment 1, ON/OFF is performed 6 times with a period of 10 seconds. In ion judgment 2, ON/OFF is performed 10 times with a period of 1 second. Then, when the difference (the amount of change) between the maximum value and the minimum value of the output voltage of the measuring part 67 is greater than a given threshold value, the presence of ions is concluded respectively. |
