| 摘要 |
PURPOSE:To prevent mutual interference and malfunctions due to a harmonic noise of a commercial power source by operating plural detectors, which are installed adjacently to one another, with an oscillating circuit which oscillates the frequency where an integer-fold frequency of the frequency of the commercial power source is added to a fundamental oscillation frequency. CONSTITUTION:An oscillating circuit 11 oscillates a fundamental oscillation frequency fo and detecting signal frequencies f1 and f2 obtained by adding integer- fold frequencies of the commercial power source frequency to the fundamental oscillation frequency fo. If the beat frequency between these frquencies and the power source harmonic noise is a problem, the fundamental frequency fo is shifted, and detecting signal frequencies f1 and f2 are shifted also in accordance with this shift. Detectors 10a, 10b, and 10c adjacent to one another perform detecting operations with respective detecting signal frequencies f0, f1, and f2. They are provided with detecting lines 3a, 3b, and 3c. Consequently, malfunctions due to beat between requencies of detectors 10a, 10b, and 10c installed adjacently to one another and malfunctions due to beat between these frequencies and the harmonic noise of the commercial power source are prevented. |
