| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect the passage of a vehicle more surely as compared with a conventional method using a single threshold value. SOLUTION: A first reference level (a first threshold value) V1u and a second reference level (a second threshold value) V2u whose level (on the side of a terrestrial magnetism level) is lower than the first reference level V1u are decided on the upper side of the terrestrial magnetism level with reference to a magnetic-sensor output. Then, when the magnetic-sensor output exceeds the reference level V1u , a vehicle existence signal is judged to be 'existing'. When the magnetic-sensor output exceeds the reference level V1u and it then becomes less than the reference level V2u , the vehicle existence signal is judged to be 'nonexisting'. Thereby, the vehicle existence signal does not become a level '0' between the time t2 and the time t3 , and it is possible to prevent the passage of one vehicle from being detected erroneously as the passage of two vehicles.</p> |
