Magnetometers

[Ocean7]

anyone ever use a Magnetometer on land and what could it reasonably be expected to find
What will it not find? Thanks!

[Charles,Oak Island]

Ocean7 a mag will help you find ferrous metals. If you scroll down to Techniques, then to my reply on Cheap Magnetometers. Read the article about Wadsworths home built differential proton magnetometer it might help some. I will share any info I have on mags.
I am planing to build one for land use this winter. I have one for boat use.

[Charles,Oak Island]

I borrowed this from Dan's web site, I don't think he will mind..


What is a Proton Precession Magnetometer?

A magnetometer is an instrument used to measure the strength of a magnetic field. Magnetometers are used to measure variations in the earth's magnetic field in order to locate mineral deposits, achaeological sites, buried treasure, or submerged objects such as submarines or shipwrecks. The proton precession magnetometer operates on the principal that the protons in all atoms are spinning on an axis aligned with the magnetic field. Ordinarily, protons tend to line up with the earth's magnetic field. When subjected to an artificially-induced magnetic field, the protons will align themselves with the new field. When this new field is interrupted, the protons return to their original alignment with the earth's magnetic field. As they change their alignment, the spinning protons precess, or wobble, much as a spinning top does as it slows down. The frequency at which the protons precess is directly proportional to the strength of the earth's magnetic field. This is the Proton Gyromagnetic Ratio, equal to .042576 Hertz / nanoTesla. For example, in an area with a field strength of 57,780 nT (such as my home), the frequency of precession would be approximately 2460 Hz.

In a simple proton precession magnetometer, a bottle of fluid rich in hydrogen atoms, usually distilled water or a hydrocarbon such as kerosene or alcohol, is surrounded by a coil of wire which can be energized by a direct current to produce a strong magnetic field. When the current is shut off, the precessing protons induce a very weak signal into the same coil, which is now connected to a suitable output device. This output circuitry may be a frequency counter calibrated to give a direct readout of of magnetic field strength.

[Ocean7]

ok thanks. How large does object have to be? How deep does it read in ground?

[Charles,Oak Island]

from the manual of my trust ole MX500:

Ferrous material
1kg (2.2 lbs) 2m (6.5ft)
10kg (22lbs) 4m (13.1ft)
100kg (220lbs) 10m (32.8ft)
1 ton (2240lbs) 21m (68.8ft)
10 ton (22400lbs) 46m (150.9ft)
100 ton (224000lbs) 100m (328ft)

I did a quick guesstamate on lbs and ft conversion so may be off a little

[bakergeol]

Hi Ocean 7
The folks above have already filled you in to the useage of mags. If I was considering one for land use e.g. locating an iron chest I would probably buy one of those utility locators used for pipe location. Fisher still sells 2 models. Actually I would recommend the Magnawand which can distinguish flat buried trash from objects with depth(drums, chests).


I own a Mag(Ferrous Hound) but it is designed to be used with my netal detector as the senor attaches to the search coil. I plan on using it on mine dumps looking for gold. I hunt in all metal mode and when I get a hit I turn on the mag to check for ferrous content. The mag will tell me if my target is iron,? a hot rock or a iron rich specimen(usually magnetite). If I find an ore specimen that screams on all metal mode and silent on the mag-I have an ore specimen(I believe besides gold the metal detector can signal on galena also).

George

[Charles,Oak Island]

George,
do have an idea of the price range on those ?
thanks

[bakergeol]

Hi Charles
The Fisher FP-10 sells for around $715 Magna-trak $589. Schonstedt sells quite a few models. You see them on E-Bay-usually sell quite well too.

The Magnawand site is http://magnawand.com
For companies that sell them just type in magnawand on any search engine. I saw one that sold for $675 today but I believe there are some outlets that sell them a lot cheaper.It is made in Canada- so for a good price I would check with Canadian outlets. If memory serves me I believe I saw a Canadian outlet that sold them for $500. It's ability to distinuish flat trash iron from iron objects which have depth to them( e.g.drums) is unique.This will be important when you start digging. It will detect a manhole cover at 10 ft. I have always wondered if the Magnawand could distinuish a cannonball from a flat piece of trash?

The Ferrous Hound's site is
http://www.reevejones.com.au/about.html
The cost was $489- It also took me also 2 months to obtain one. This mag was designed to be used with PIs(Pulse induction) metal detectors in Australia which have no or ineffective iron discrimination to afford some method of iron discrimination.You attach the sensor to the search coil and hipmount the control housing.This mag is more sensitive to small iron and does not have the depth of the Magnawand. Mags of this type(including the magnawand) are insensitive to small? flat thin pieces of metal. Notice the Magnawand's depth is for PK nails which are very long. For example a 1943 steel penny will only be detected at 2" with the Ferrous Hound but a 1/4" bolt 1" long will be detected At 11". The Ferrous Hound will not replace VLF discrimination but it will serve me well for my applications.

George

[Charles,Oak Island]

George,
thanks for the info. Guess I will stick with building (about $125) since I have more time than money for a second mag.

[Charles,Oak Island]

I am going to post Phil Barnes web site in case anyone wants to read more and get some info on plains. I think I am going to order his cd and build his this time.



http://members.aol.com/phil770/index.html

[amxgerry]

hey charles


could you post a link to dans site (please)

does anyone ellse have any links or sites for finding bedrock depth, black sand deposits, or any other ways of prospecting for placer gold other than digging or metal detectors.

thanks gerry @ bc canada.

[Charles,Oak Island]

http://www.portup.com/~dfount/proton.htm



http://members.aol.com/phil770/index.html

[amxgerry]

thanks very much


gerry

[Charles,Oak Island]

Gerry,
keep me posted on your progress.
Charles

[amxgerry]

hi charles

well... the bottom line is = the more i read, the more confused i get...lol...


i have several things i want to do! i have a placer claim in cariboo b.c. canada.

i have very rusty , highly mineralized water coming out of several spots on a hillside, that i want to trace or follow to where the water is picking up the minerals. will the magnetometer do this easily?

i want to find large black sand deposits.

i allso want to locate bedrock, clay layers, and gravel layers inbetween, with electronics, as digging is too pricey to just dig test holes all over the place and allso permits are required etc. etc.

it sounds like seismics or gpr are the way to go, for that, but allso very pricey and i may not be able to determine the results.


of course the end result is too find placer gold.

is the magnetometer easy for a dummy to interpret, and use, as the kit is very reasonable priced, but i see there is dozens of different units out there.



thanks gerry