| 摘要 |
PURPOSE:To distinguish person from object certainly by installing piezo element on a seat or bed, calculating at unit time intervals the rate of emergence at which the output signal from piezo element exceeds a certain specified value, and thereupon judging if the seat, etc., is occupied. CONSTITUTION:When a person is seated, a piezoelectric element 1 installed on a seat 6 defroms, and the voltage generated by piezoelectric effect is filtrated by a filter 2, amplified by an amplifying means 3, and smoothened by a smoothening means 4. First comparing means 7 compares the output V of the smoothening means 4 with a predetermined value Va and emits Hi-signal if V>=Va and a Lo-signal if V<Va. The first comparing means 8 calculates the rate of emergence per unit time of Hi outputs given by this first comparing means 7, while the second comparing means 9 emits Hi if the rate of emergence per unit time exceeds the second preset value and emits a Lo binary signal if below the second preset value. It is judged as occupied if this output is Hi and as not occupied if Lo. |
