A wheel sensor that is particularly suited for track release signaling systems has at least one sensor device having an AC-fed sensor coil of an electric oscillating circuit sensitive to an inductive interaction of the sensor coil with passing wheels of rail vehicles. A further spool is connected to the sensor coil for suppressing external interference fields in a counter circuit. The further coil is arranged underneath the sensor coil and a spacing distance between the further coil and the sensor coil is at least one third of the inside diameter of the sensor coil.
1. A wheel sensor with at least one sensor device, comprising:
a sensor coil, operating on alternating current, connected in an electrical resonant circuit that is sensitive to an inductive interaction between said sensor coil and a rail vehicle wheel rolling past said sensor coil, said sensor coil having an internal diameter; and
a further coil disposed underneath said sensor coil, connected in an opposite sense to said sensor coil, and operative to suppress external interference fields;
said further coil being disposed at a spacing distance from said sensor coil, said spacing distance amounting to at least one third of said internal diameter of said sensor coil;
said further coil having a longitudinal axis extending coaxially with said sensor coil.
2. The wheel sensor according to claim 1 in combination with a track-free signaling installation.
3. The wheel sensor according to claim 1 , wherein said further coil has a longitudinal axis extending parallel to a longitudinal axis of said sensor coil.
4. The wheel sensor according to claim 1 , wherein said sensor coil is an air-cored coil.
5. The wheel sensor according to claim 1 , wherein said further coil is an air-cored coil.
6. The wheel sensor according to claim 1 , wherein said further coil and said sensor coil are of a mutually different type.
7. The wheel sensor according to claim 6 , wherein said further coil and said sensor coil have mutually different geometry.
8. The wheel sensor according to claim 6 , wherein said further coil and said sensor coil have a mutually different number of turns.
9. The wheel sensor according to claim 1 , comprising at least two sensor devices disposed at a distance from one another along a longitudinal direction of a rail, with respect to a wheel sensor mounted in a region of the rail.