[ List Subjects ][ Main Page ]
[ View Followups ][ Post Followup ]

Date: 02/21/02 at 9:39 PM
Posted by: Russ Kincaid
E-mail: russlk@yahoo.com

In Reply to: metal detector coils posted by M Hunt on 02/21/02 at 7:29 PM:

The shield provides a constant capacitance to ground. Otherwise, the capacitance will vary with height above ground causing detuning of the oscillator.
Petrolium jelly is an inexpensive insulator and repells water. It is used to weather-proof the coil.
The oscillator needs a particular inductance, which is determined by the diameter, length and number of turns of the coil. I believe the extent of the field depends on the diameter: The larger the diameter, the larger the field.
A coil can be "scramble wound" or wound in a cris-cross pattern to minimize capacitance, but I don't think that is important in this application.
I don't know anything about passive receive coils.

Follow Ups:

  Re: metal detector coils M Hunt   Posted at: 02/25/02 (0)

Post a Follow-up:

Name:
E-Mail:
Subject:

Message to Post: