WHEEL DIP

When a wheel passes between Tx and Rx coils, the magnetic flux path gets disturbed
and induced voltage in the Rx coil reduces substantially. The drop in the Rx coil output under
the influence of wheel is called “Wheel Dip”. Wheel dip depends on several factors such as type
of wheel, rail profile and type of sleepers and orientation of wheel in relation to transmitter and
receiver coils. Fig: No 2.3 shows 4 types of wheel dips.

Wheel dip adjustments enumerated above are made by changing the position

transmitter body on the rail clamp by moving forward or backward and serving the receiver coil
signal on multi-meter when a dummy wheel is moved over the track device.
A dummy wheel is a metallic plate which when placed on the rail in between transmitter
and receiver coil , causes a ‘Dip’ in the receiver coil signal similar to one caused by an wheel. A
dummy wheel has graduated markings to enable it to be set for the type of rails to which track
devices have been fitted. For 52 Kg rails, proper wheel adjustment is obtained by setting the
dummy wheel at 52 mm mark.