Carls mag, what you must know.

[fitz]

Maybe everybody gets this and I am just stupid but maybe not. When you put the sensors into the tubes they must have perfect alignment. You MUST also have them rotated the same. I did not do this at first and I could not get them to align very well. I did not read anything in the plans about it, but it makes a big difference.
Here is a crude pic but I think you can get the idea. It is looking at the pin ends of both sensors. I also put the foam rubber in right when I start to use the mag. I remove it after each time. It takes a bit more time but the rubber just gets squished and stops working if you leave it in.

[damiafix]

Hi Fitz,
please, can you share some picture of your mag? It work fine?

Cheers, D.

[epitopios]

dear Fitz, you mean that the 4 terminals of each sensor must be horizontal and not vertical to the earth ??

[fitz]

The terminals

I don't think it matters how they are turned as long as they are the same. Vertical or horizontal or somewhere in between. Just get them the same. I could not get a good balance until I fixed this.

[damiafix]

Hi Fitz,
please, can you tell me if you've aligned the two sensors of your probe?
Do you've misured the tension between the pin 14-15 of the DAC? The value?

Cheers, D.

[Krzysztof]

The terminals

I don't think it matters how they are turned as long as they are the same. Vertical or horizontal or somewhere in between. Just get them the same. I could not get a good balance until I fixed this.

Hi Fitz.
I disagree.
The probe Measures the magnetic field component along its long axis.
How do you want to look for something under the surface of the Earth, the probe Should Be Placed in the same vertical axis - Easy Interpretation of results.
Any deviation from the vertical gradiometer During the measurements, gives, unfortunately, a large deviation.
Best regards Chris.

[fitz]

Yes But..

As a practical matter my finished mag could not locate a large pipe that is less than 1 foot deep. I did not measure the voltage at all. I did connect an audio frequency counter to the output. As I rotated the mag it had a huge variation. The only adjustment I made was to rotate one sensor to match the other. I was then able to get the frequency to null out (less than .005hz) as I rotated the mag. Then the pipe was easy to locate from more than 4 feet away. I also have used the mag to detect graves in a grave yard. Most of these graves are very very old and I could detect the edges of the grave with no problem. So although you are right in you idea, I know what fixed my mag. So who knows... I do think the use of the mag is not 100% science. it takes some amount of art also.. I really am thinking of building another now that I have learned so much from all of you, Thanks.
fitz.

[damiafix]

I think that Fitz, say that in the alignment phase, the sensors should to be oriented at the same level and inclination (specifically with the pins oriented in the same direction), but (as we can learn from the literature) is clear that in the research phase, the probe should to form a 90° angle with the earth, vertically for the best performance; in this I agree perfectly with Chris.
Refered to the your mag, Fitz, many compliments I'm glad that it work fine; my project is going slowly, becouse I've some problem. I'm checking the connections, and the integrity of the IC (as you read from this 3d).
Could you share some picture of your gradiometer, I'm very curious!

Cheers, D.

[fitz]

Yes But..

Yes 90 degree with earth, but the rotation of the sensors (along each sensors long axis)is what I am talking about. I would send a pic but I would have to take the mag apart to do it. The sensors must be vertical and 100% in line and rotated the same. Maybe I will make a short utube video, that will help clear it up.

[damiafix]

Dear Fitz,
a video could to clarify any doubt!

Many thanks for your help, D.

[Krzysztof]

Calibration

Hi Damiafix.
If you will permit, then I will show, as I understand "Calibration". On desk and by hand but I came back with works near home garden just and beer drinks.
Fot1. Ideal situation; unreal, because manufacturer FGM3 does not sell them evaporated; they differ with frequency and inclination profile (tenderness, sensitive).
Fot2. Very bad!. Frequent mistake. FGM stood one should to be in line W / E it because was can in one point get apparent equilibrium, and to get in 2 different places about several degrees 0Hz even. Control and prevention how in Fot5.
Fot3. Regulating get one FGM minimum Hz / V in line W / E. Seem oneself, that procedure construction from square of Al Fitz it is risky, is sure Al this diamagnetic le rotational currents near frequency FGM about 75kHz 1 cm from axis of coil will give already to know and this causes inequality. I think construction Panzerfaust and Geo despite trouble is safe. This only my modest sentence.
Fot4. They in my construction of probe be placed in rolled out artist, I think in good axis. I regulate turning over on minimum one probe about 180 degrees unfortunately, my probes also oneself they differ a bit.
Fot5. Final control then turn MAG about 180 degrees in line W/E tell about completely . Evidently assembled device. They nearer zero by whole turn this larger congratulations for constructor!
Fot6. We do not to leave behind, that our measure has something to measure also, bringing nearer on distance metal tweezers for example 10 cm should already cross measuring range. At me MAG standing 50 cm on radiator of central heating crosses measuring range on LED also.
Fot7. It was can variously construct MAG how in Fot7a (Fitz, Geo, Panzerfaust) or Fot7b (Krzysztof) or Fot7c - control is difficult here near large tenderness the change of putting measure will alter indication already a lot of how in Fot5.
Fot8. Of measurement perpendicular position. Because, component perpendicular it is in Europe magnetical field about 45mikroT, and component horizontal 20mikroT, then every the smallest deviation from plumb - line is effective with large measuring mistake. Additionally receiver on head (some good types magnetodynamic contain solid magnet - which is already near measurements impertinence MAG), times indispensable telephone portable, batteries in metal casing. Construction Fitz possesses measure (interesting, or magnet has ?). Standing by MAG operator is not transparent also nor virtual - therefore I support Fitz - measurements then art! The Geo proposed the location between probes the small of magnet the aim of calibration recently, I do not agree, we measure very small the change of field caused through buried artefacts - about then it walks us all here - so introducing in field of measurement any magnet all will spoil. I as signalizer use small piezo on 3V it - is not amazing, but safe.
Fot9. How I noticed previously, it gets the smallest deviations measure in one direction only. I saw on Yutube the money transfers of video from OKM today and I fell on this, that them the alternant mountains and the valley on these pretty offences 3D this can be the reason of measurement in both directions - this would be the joke.
I finish and I wait on constructive criticism. I greet all constructors.
Best regards Chris

[damiafix]

Dear Chris,
many thanks for your reply, I'm sorry for the delay I was away.
Your hand scheme is great, and I've understood perfectly your Calibration procedure; I agree totally with you. Finally someone that show clearly the calibration procedure!
Unfortunately, in this moment I can't to test it, my gradiometer have some problem, as you can read here.
I'm looking to replace the AD557, becouse I read a tension superior of 2,5 volt at the pin 16; it's also 4,5 volts, sometime; what do you think, it could to be damaged?

Cheers, Dam.

[epitopios]

Dear Chris,
many thanks for your reply, I'm sorry for the delay I was away.
Your hand scheme is great, and I've understood perfectly your Calibration procedure; I agree totally with you. Finally someone that show clearly the calibration procedure!
Unfortunately, in this moment I can't to test it, my gradiometer have some problem, as you can read here.
I'm looking to replace the AD557, becouse I read a tension superior of 2,5 volt at the pin 16; it's also 4,5 volts, sometime; what do you think, it could to be damaged?

Cheers, Dam.

Dear Damiafix
did you find something else to change it or by a same ??
any news ?
regards , epitopios

[damiafix]

Hi Epitiopos,
unfortunately I've still this problem, here it's very hard to find a AD557 replacement, and from the check, the circuit seemed to be ok, so I was a little discouraged. It's much time that I don't continue the check on the circuit.
I hope to continue in the next weeks, in the first days of my holidays, with the intention of to understand what don't work.
I would to thank again Chris for his help.


Have a good day, D.

[Krzysztof]

Hi Damiafix.
I'm still waiting for an answer, what happened in your MAG: PIC or AD557, maybe think about a little upgrading, renewal? Do you have access to small micro and LCD? You are not the only ones with problems with the MAG, we could collectively come up with something.
Best regards Chris.