| 摘要 |
PURPOSE:To adjust the sensitivity of a passing car detecting loop coil automatically by controlling the threshold of detecting levels on the basis of the average value of plural cars. CONSTITUTION:When a car passes through the loop coil 1, its inductance is changed, the changed value is detected by a changed value processing part 2 and the detected result is supplied to a signal processing part 6. The processing part 6 decides the kind of an automobile or the like from the detected result pattern, calculates the average value of the detected results of the fixed number of cars belonging to the same kind to control the threshold of the detecting levels in the coil 1. Even if the sensitivity of the coil 1 is changed, the sensitivity is automatically corrected, so that it is unnecessary to stop the car and adjust the sensitivity of the loop 1 manually every fixed period. |
