| 摘要 |
PURPOSE: To prevent missensing by sensing the inter-extremal period, from the maximum to minimum, of the magnetic field horizontal component of a magnetic substance laid on a road and also the peak time of the vertical magnetic field, and emitting a sensing signal only when the peak value lies within the inter-extremal period. CONSTITUTION: The horizontal component and vertical component of a magnetic field formed by a magnetic flux generated by a magnetic substance are sensed by a horizontal magnetic field sensing coil 13H and a vertical magnetic field sensing coil 13V. The inter-extremal period from the time, when the sensing signal of the coil 13H shows the maximum, to the time it shows the minimum is sensed by inter-extremal period sensing parts 20, 22-25, 27, 28. The peak value of the sensing signal given by the coil 13V is sensed by peak time sensing parts 21, 29. If the peak time lies within the inter-extremal period, an output pulse forming part 31 judges the applicable signal is a proper signal not containing any noise component and emits a sensing output signal. Thereby noise included in the sensing signal can be excluded. |
