Pulse Induction Coil Data

Single Coil

Revised 10/16/2006

Winding: Coil is aproximately 40 turns, No. 28 Awg. Either wound in a round
shape, square or in a rectangle! A Diameter of about 6 to 8 inches is about
normal. In a Rectangle, Optimum is about a 4 to 1 ratio, length to width.

Some guys using my detector have wound coils up to 4 Feet Square for deep
searches of large objects! These large coils are usually only 4 turns or so!

Each has its advantages and disadvantages! Also more turns and bigger wire
equils a greater magnetic field. But don't go overboard.
Even very small coils of a "1 inch" diameter can be useful!

Low Capacitance is important in the coils. This can be further acomplished
by winding the coil in a single layer spiral. It's not too easy to do,
but it can be done and will make your unit much better.

Here are some test that I have done on wires in the 22AWG to 18AWG range:

1) Two parallel wires, close together, 1 foot long 18AWG = 42 Pf.

2) Two parallel wires, close together, 1 foot long 20AWG = 39 Pf. 

3) Two parallel wires, close together, 1 foot long 22AWG = 36 Pf.

These tests were done at a frequency of 1000 Hz.

This Only affects Direct Parallel Wires, But does not Coils in the same manner.


However, Capacitance can greatly reduce the effectiveness of the coil!

Finishing: After you are happy with the coil, it is important to lay the
coil on a solid piece of NON-METALIC material and EPOXY it so it is RIGID.
As small amounts of movement within the coil can affect performance a bit!

Also make sure the Wire leads coming from the coil, go out horizontal,
Not directly Above or below the coil!



Dual Coil, Cancelling Design

Two coils have the advantage of "Noise Rejection" should their be unwanted
interferance in the vacinity of your search! One coil does the search,
While the other coil cancels noise and simular signals.
Particularly useful if it is to be used near Power Lines or soil
containing a lot of iron deposits!

If two coils are used, they are easiest done round. Wind both identical
and overlap them up to about 50%, but not greater than. Keep both wound
in same direction when overlapped! The Less the overlap or no overlap,
will results in a smaller confined field of search, covering less area.

Follow the Winding and Finishing Instructions for the Single Coil as well
as the info here that is related specificially to the Two Coils!

Dual Coils, Seperate Recieve & Transmit

This Coil Configuration allows the transmit coil to be constructed for
maximum magnetic field with a fairly heavy wire, while using a recieve
coil with more turns of smaller wire for better pickup.

Picture Of one of the Coils I made.




All Imformation in this Article is "Copyright protected".

 Chemelec 
 *Copyright © 2003 & 2006*