BY LAAASHIKA ECE A SEC In this method Voltage required for sensefinding is given to the loop circuit When metallic objects are present it produces undesirable voltages in the loop Voltages with ID: 217874
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Slide1
AN AURAL-NULL DIRECTION FINDER
BY:
L.A.AASHIKA
ECE A SECSlide2
In this method, Voltage required for sense-finding is given to the loop circuit.
When metallic objects are present ,it produces undesirable voltages in the loop.
Voltages with
quadrature
phase broadens the null.
So , in this method we are going to introduce a
quadrature
voltage that is adjusted to cancel the picked up voltage.Slide3
INPUT CIRCIUT OF AN AURAL-NULL DIRECTION FINDERSlide4
Working:
For loop
voltage,there
is a series tuned
circiut,whereas
an additional voltage is introduced by a variable inductive coupling b/w L1 & L3 with switch in position 1.
With the help of C2,L5,C3 the new voltage becomes in phase
quadrature
with the loop voltage.
Using L1 &L3, the
quadrature
component from “antenna effect” can be cancelled out.Slide5
working
When the switch is in position 2,the current in L4 is in-phase with vertical antenna voltage and voltage in L2 is in phase
quadrature
to it.
By adjusting R1,a good sense discrimination can be obtained.
So when switch is in ‘balance’ position,L3 inductor sharpen the null whereas when it is in ‘sense’ position, the loop is turned to 90 degree and the sense can be found out.