Device for determining the presence of a vehicle by means of a magnetic core probe

摘要

Device for determining the presence of a vehicle by means of a magnetic core probe, it being the case that both given overshooting of a prescribed positive, as well as given undershooting of a prescribed negative deviation of the measured field strength as compared to the field strength of the undisturbed field, a signal indicating the presence of a vehicle is emitted, and the emission of the signal characterising the presence of a vehicle is extended in time after the value of the measured magnetic field has reapproached the field strength of the undisturbed field, which device is characterised in that the extension time of the display increases with the preceding unbroken duration of display and/or the time between the response of two detectors following one another in the driving direction, the extension time being smaller than the preceding duration of display, or in that the extension of the display increases with the increase in the gradient of the value of the field strength in the event of reapproaching the undisturbed field strength.