mag. sources

[vlad]

I am a long time metal detector user, but know nothing about magnetometers.
I recently saw a program where a USAF TEAM was using what they described as a 'gradiometer mag.' to locate unexploded bombs; they went on to say it consisted of 2 mags., one stacked atop another, and that it read only the ground beneath the 'antenna,' which was a long "L" shaped device.
I need something strong and localized, and have already tried the FISHER FX-3
MAG. STICK, but it did not have the range.
Can anyone recommend some models, and sources?
sincerest thanks, TIM

[Cyberstace]

Mag sources

See http://www.speakesensors.com/

[schatzsucher]

Or this

http://www.stefan-mayer.com/Lcsing.htm

This sensor use OGT!

[Goldfinger]

Hi Vlad: The Magnawand is touted to have a very deep search capability. No personal experience, though. Thanks for the feedback on the Fisher. Well, another one bites the dust. If you come up with anything, please let me know. Best wishes..

[Goldfinger]

Hi vlad: This company looks like a good bet: http://www.quantrosensing.com/index.html

[Unregistered]

The original poster was asking for a gradiometer. I don't see where Quantrosensing sells anything but single sensor units.

[Unregistered]

The Fisher is good for detecting manhole covers very near the surface and ignoring smaller ferrous clutter.

For deep searches of ferrous objects on reasonably low cluttered properties, see www.magneticlocators.com DML 2000m ($700). Call or Email Warren Dunham about your application. I know it will work to at least 29' deep but you have to hold the stick in the direction you want to sense.

If the site has lots of metal junk and clutter and the target is deep then you will need a more specific strategy. If your target is large (like a buried drum under wads of barbed wire) and/or directional (like a buried, abandoned, & presumed vertical, steel-cased water well under barbed wire), then surveying first with a proton mag is usually a good method. Proton Mags see thru the smaller clutter and you don't have to hold the sensor in any particular direction. The Qs works but it is a little funky, the meter on the land mag is upside down and the large liquid filled sensor at the other end of the 40" PVC tube gets pretty heavy in a hurry. And if the target has a strong gradient (>1000 g) then your anomaly will be indicated by the meter reading "ERROR". But if keeping costs down is imprtant then for the $ try the Qs kit ($600) and make your own modifications (like put sensor in backpack and carry controller). But if there is heavy equipment involved and other people's time /$ then the Qs might not make the best impression to clients. In that case call GISCO speak to Dr. Tweeton or John Nelson about the GEM 19TW ($7700).

[Unregistered]

The original poster was asking for a gradiometer. I don't see where Quantrosensing sells anything but single sensor units.

Hi Vlad and unregistered guest: Sorry, my bad. (I must of missed that part about a gradiometer.) Heck, I don't even know what a gradiometer is!
Best wishes finding one.

[Goldfinger]

Hi unregistered guest: Thank you for your input on this. I found out that the Fisher, and other mags, are not good for what I am looking for. I did check out locators.com. I also found an interesting detector at that link I left above. I'm going to have to check out that device more.
But you are helping me get on the right track. Thank you again...

[rgecy]

vlad,

I would have to recommend the EPE Magnetometer (Gradiometer) Design. It consist of two Fluxgate Mag Sensors and will detect local anamolies directly beneath the bottom sensor. It is held vertically and a grid is walked to cover an area. The unit has a data logger and gps input and logs the data to be viewed later on a computer. You can also see the reading in real time, but no audible response.

Carls design also functions very well and can have a real time audio signal to determine when an object is detected. Both units use the Speak Fluxgate Mag Sensors and are highly recommended if you are looking for an inexpensive unit.

I have built both units and they both work great! The down side is, you will have to assemble and calibrate them yourself. But thats where the fun is!

Good Luck,

Robert in SC

[Unregistered]

Hi Vlad and unregistered guest: Sorry, my bad. (I must of missed that part about a gradiometer.) Heck, I don't even know what a gradiometer is!
Best wishes finding one.

The gradiometer is simply a magnetometer with two sensors spaces some distance apart.

What happens with magnetometers is that the sensor(s) pick up signals
from magnetic storms, power lines etc..

If you have two sensors the signal from each sensor is mixed (just about like the old beat frequency detectors) and you get the difference in the signal from both sensors.

So if both sensors are getting the same unwanted signal from a magnetic storm, power line or what ever, the signals are beat one against the other and it is cancelled out.

If one sensor is closer to a FERROUS object or another anomily (magnetic ore body, basalt, black magnetic sand, andesite, meteorite, iron deposit etc..) that affects the earths magnetic field, the signal from that sensor will get through since there is no equivalent signal reaching the other sensor to cancel it.
Don

[Unregistered]

Or this

http://www.stefan-mayer.com/Lcsing.htm

This sensor use OGT!

Could a 1nT (or even 0.5nT if the signal was sampled very near the sensor) resolution Gradiometer be realised using these?

Is there a price in small numbers 2 or 4's

thank you.

[oldkidnewtoy]

I'm currently looking at their FLC 100-70 which has a 70 µT range and better linearity. It’s worth noting that they have an analogue output unlike the Speake FGM-3 so noise may be an issue depending on your application.