The
sensor consists of a 50cm long ‘PVC’ pipe, with 5cm external diameter. We
wrap three layers of 0.04’’ “MuMetal” sheet around the pipe. Over the
“MuMetal”, we wrap insulating tape and coil enamel coating wire, 1 mm thick,
at pipe’s length. We coil ~9 layers of wire (~ 4.500 coils).
When
the coil is completed, we wrap it up with insulating tape and plate it with
aluminum foil or self-adhesive aluminum tape.
The aluminum is connected to the plate of the coaxial cable (RG-213,
RG-8…) that we use as signal transfer line.
The
end of the external winding of the coil is also connected to the shield of the
cable, while the internal end is connected to the internal conductor of the
coaxial cable.
The
coil in inserted into a 60cm long ‘PVC” pipe, with 10cm diameter it is then
stabilized and waterproofed.
The
coil has pure resistance R = 16 Ohm and self-induction L = 1 H. The final construction is placed horizontally 10cm above the
ground and stabilized. The ends of
the coil are adjusted at 110o and 290o respectively in reference to the magnetic
north.
Just
to emphasize that the coil should have low pure resistance (including the
coaxial cable), in order to achieve reduced noise in the circuit.
