| 摘要 |
PURPOSE:To reduce influences of temperature, humidity, or the like by substituting the variance of a stray capacity between a sensor consisting of an electrode member and an object to be detected with the variance of a frequency signal and detecting the frequency signal and viewing the fall state of a detected voltage signal to detect the approaching state of the object. CONSTITUTION:In an object detector, a differentiating circuit 9 which performs the differential processing of a detected voltage signal Vd' is provided in the preceding stage of a voltage variance detecting circuit 6. Time constants of delay elements Rd and Cd in the circuit 9 are set to large values to eliminate long-time variance components due to the change with time of temperature, humidity, or the like included in the detected voltage signal Vd'. The circuit 6 consists of a delay differential circuit 61 and a decision circuit 62 which decides whether the time width of an output signal Vo of the circuit 61 is longer than a preliminarily set value or not, and the circuit 62 judges the entrance of the object into a dangerous area to give an alarm command to a driver when the time width of the output signal is longer than the prescribed value. |
