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# Metal detector recommendations?

B

#### Bruce W...1

Jan 1, 1970
0
I've always wanted a metal detector. Not so much for treasure hunting
but for utility purposes like maybe tracing a buried wire, tracing a
conduit in a wall, finding the bolt I just dropped in the lawn, that
sort of thing.

I know more about ground penetrating radar than I do about consumer
metal detectors. On ground penetrating radar I know that, for my
purposes, I can't afford it.

Metal detectors, to my knowledge, were first used in WWII. From an
appearance standpoint I don't see much difference from current consumer
model. Has there been any evolution?

I find metal detectors that sell from between $50 and$300. Is there
much of a difference? Do lots of LED's or analog meters serve much
purpose? Can they really detect different types of metals?

What is the state of the art of metal detectors? What do they do well,
and not so well? What is their detection range in dirt?

Can you make any recommendations on a good model? Does one stand above
all others today?

Thanks for your help.

R

#### Robert Baer

Jan 1, 1970
0
Bruce W...1 said:
I've always wanted a metal detector. Not so much for treasure hunting
but for utility purposes like maybe tracing a buried wire, tracing a
conduit in a wall, finding the bolt I just dropped in the lawn, that
sort of thing.

I know more about ground penetrating radar than I do about consumer
metal detectors. On ground penetrating radar I know that, for my
purposes, I can't afford it.

Metal detectors, to my knowledge, were first used in WWII. From an
appearance standpoint I don't see much difference from current consumer
model. Has there been any evolution?

I find metal detectors that sell from between $50 and$300. Is there
much of a difference? Do lots of LED's or analog meters serve much
purpose? Can they really detect different types of metals?

What is the state of the art of metal detectors? What do they do well,
and not so well? What is their detection range in dirt?

Can you make any recommendations on a good model? Does one stand above
all others today?

Thanks for your help.

There are various designs, crudely put into 2 classes:
a) transmitter coil perpendicular to receiver coil, typically a harness
over the shoulders is used, with one coil in front, and the other in the
rear. I think Fisher was the first with this design, and this is good
for pipes and other large objects in the ground and goes fairly deep as
i understand.
b) both coils are in one circular "pad" at the end of a stick ling
enough to use as a ground scanning wand.
This is the class of detector you want, but there are many variations,
from low frequency to unstated but not low frequency. Some use square
waves, some use pulses, and some use sine waves.
Many of the modern ones use a microprocesor to interpret phase shift
and signal loss in order to better "discriminate" between one metal and
another.
The two best makers are White and Garrett.

T

#### Tsvetan Usunov

Jan 1, 1970
0
Bruce W...1 said:
I've always wanted a metal detector. Not so much for treasure hunting
but for utility purposes like maybe tracing a buried wire, tracing a
conduit in a wall, finding the bolt I just dropped in the lawn, that
sort of thing.

I know more about ground penetrating radar than I do about consumer
metal detectors. On ground penetrating radar I know that, for my
purposes, I can't afford it.

Metal detectors, to my knowledge, were first used in WWII. From an
appearance standpoint I don't see much difference from current consumer
model. Has there been any evolution?

I find metal detectors that sell from between $50 and$300. Is there
much of a difference? Do lots of LED's or analog meters serve much
purpose? Can they really detect different types of metals?

What is the state of the art of metal detectors? What do they do well,
and not so well? What is their detection range in dirt?

Can you make any recommendations on a good model? Does one stand above
all others today?

Thanks for your help.

a good starting point may be :

http://www.thunting.com/cgi-bin/geotech/pages/common/index.pl?page=main&file=main.dat

a lot of stuff and schematics are there

Best regards
Tsvetan

P

#### P A U L

Jan 1, 1970
0
There are various designs, crudely put into 2 classes:
a) transmitter coil perpendicular to receiver coil...
b) both coils are in one circular "pad"..
This is the class of detector you want, but there are many variations,
from low frequency to unstated but not low frequency. Some use square
waves, some use pulses, and some use sine waves.
Many of the modern ones use a microprocesor to interpret phase shift
and signal loss in order to better "discriminate" between one metal and
another.
The two best makers are White and Garrett.

Do metal detectors based on 360deg. rotating magnetic pulsed fields
(in several individual transmission loops surrounding the receive
loop) to find direction exist?

In fact what i think of is a transposed magnetic principle of the
system used in radio location "doppler scan antenna direction finding
system".
Several magnetic transmission loops (8) on the outside (switched in
sequence) and a central reception loop overlapping halve the
transmission loops (to avoid as much as possible transmitter/receiver
signal interception).
The relative phase of the outside loop switching versus the received
signal provide the metal sloop distance direction.

Paul

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