Magnetometer Project

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Carbon60
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Magnetometer Project

Post by Carbon60 » Wed Jan 07, 2015 7:13 am

Hopefully this thread will be helpful to anyone considering building, installing and operating their own Earth field magnetometer to measure solar activity and its impact on our magnetic environment.

Over the past couple of years I've created and refined a simple and inexpensive device capable of detecting extremely small magnetic field deviations at the nano-Tesla scale which is more than capable of detecting events such as CME impacts http://solarscience.msfc.nasa.gov/CMEs.shtml , solar wind fluctuations created by coronal holes http://www.exploratorium.edu/spaceweather/holes.html and 'solar sector boundary crossings' http://wso.stanford.edu/gifs/HCS.html

Examples of these events and their effects on our magnetic field can be found among my posts on this site.

Over the next few days/weeks Mike G and I are going to go through and document the process of building a magnetometer step by step which I hope will be of interest.

For anyone in the teaching profession, I'd strongly encourage you to consider this as an educational project for your science classes.

Stu
Lunt LS60THa B1200 PTFT
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DMK41, Basler acA1920-155
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Re: Magnetometer Project

Post by marktownley » Wed Jan 07, 2015 7:15 am

Watching with interest :)
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Re: Magnetometer Project

Post by Derek Klepp » Wed Jan 07, 2015 10:32 am

A great addition for this site Stu

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Re: Magnetometer Project

Post by Montana » Wed Jan 07, 2015 11:57 am

I really wish I were clever enough to do this, but also I don't think my garden is well suited either. I have some electric power lines about 10m from my garden, would this render it impossible?

Alexandra

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Re: Magnetometer Project

Post by Carbon60 » Wed Jan 07, 2015 12:24 pm

Montana wrote:I really wish I were clever enough to do this, but also I don't think my garden is well suited either. I have some electric power lines about 10m from my garden, would this render it impossible?

Alexandra
Hi Alexandra,

The power lines would make it a challenge, I think. My magnetometer recognizes my car on and off my driveway, which is also about 10m from where the sensor is located. Literally, the presence of my can distorts Earth's field sufficiently to be detected by the device, such is its sensitivity. Power lines would likely do the same although it would depend on the current running through them.

A quiet magnetic environment and good temperature stability (hence the need to bury the sensor under ground) are essential when aiming for reasonable accuracy.

BTW, the set up is really simple and most of the work required has been in refining the excel spreadsheet used for data analysis, which will be made available by me to anyone wanting to build one of these.

Cheers

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by Carbon60 » Wed Jan 07, 2015 12:38 pm

BTW, I found this on the net....
Power line magnetic field.jpg
Power line magnetic field.jpg (50.46 KiB) Viewed 2665 times
I will be helpful to anyone with similar issues with power line proximity. Given that we are speaking about solar induced fluctuations in the region of tens of nano-Tesla, then power lines will certainly be a problem, with their influence depending on the type of line (kV rating) and proximity to the sensor. Underground power cables should also be taken into account.

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by Montana » Wed Jan 07, 2015 12:48 pm

I've had a look and I think it is 25KV line. I certainly can't use my compass on one half of the garden. May be the other side might be possible?

Alexandra

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Re: Magnetometer Project

Post by grimble_cornet » Wed Jan 07, 2015 4:45 pm

Thanks Stu, I'm glad I don't have a power line within 100m or so - looks as if it would make a real mess of any attempt to detect solar induced fluctuations :o

I now have the basic parts so will have a read through the documentation before making a start :seesaw
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Re: Magnetometer Project

Post by swisswalter » Thu Jan 08, 2015 5:50 am

Hi Stuart

thank you very much for opening that thread. I'll follow it very closely
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Magnetometer Project

Post by Carbon60 » Thu Jan 08, 2015 7:29 am

Thanks for your interest, everyone.

Alexandra, unfortunately I don't think it will be possible to set one up successfully in your garden, under the circumstances. :cry:

Mike, Glad the parts have arrived. You'll also need to download the frequency analysis software Spectrum Lab http://www.qsl.net/dl4yhf/spectra1.html

First thing should be to connect everything together and demonstrate that everything works. Power up using batteries.

Cheers

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by grimble_cornet » Thu Jan 08, 2015 12:53 pm

Thanks Stu - I already have Spetrum Lab - I used to use it to detect meteors trails via FM radio tuner etc :?

Just about to post images of the main components - please feel free to correct any mistakes I make when describing them :oops:
Last edited by grimble_cornet on Thu Jan 08, 2015 10:44 pm, edited 1 time in total.
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Re: Magnetometer Project

Post by grimble_cornet » Thu Jan 08, 2015 2:15 pm

Firstly, let me state very clearly that I am just an ignorant duffer following instructions from Stu who has 'been there and done that' already :bow


I have been very impressed with Stu's posts over the last few months and had considered having a go at building a magnetometer myself but other things got in the way.
Then, a couple of weeks ago I saw an advertisement for a Bat Detector - a 'toy' I have always wanted to own - and it reminded me that Stu's magnetometer design used exactly the same detector........................ that was justification enough for me so I placed the order and went back to studying Stu's excellent instructions which can be found here: http://solarchat.natca.net/viewtopic.php?f=8&t=10337



OK, so here we have the main components needed to construct the basic magnetometer:

The heart of the project is the FGM-3, a Magnetic Field Sensor.
It comes in a 62mm long and 16mm diameter package with 4 terminals - 5 volt power, ground, output and an internal coil which we don't need at this stage.
This version of the sensor is sold by Speake and Co. in the UK (contact details can be seen on the image) and cost 23 UK Pounds including postage.
IMG_2851.JPG
IMG_2851.JPG (202.43 KiB) Viewed 2626 times
IMG_2853.JPG
The sensor needs a +5 volt supply and eventually this will be from a regulated mains supply but at this stage I will be using 4x1.5v cells in a battery box.
IMG_2870.JPG
IMG_2870.JPG (300.77 KiB) Viewed 2626 times
The output from the FGM-3 is a 5v rectangular pulse which varies in proportion to the magnetic field strength along the main axis of the detector. This version of the sensor is very sensitive so we need to be able to detect very small changes in the output frequency. There are several circuits designs which will do this job available on the internet but Stu has come up with what I think is a very clever alternative:
IMG_2858.JPG
IMG_2858.JPG (370.21 KiB) Viewed 2626 times
IMG_2857.JPG
IMG_2857.JPG (332.06 KiB) Viewed 2626 times
The above images show an Ultrasonic Transducer - a device which converts the output from the FGM-3 into ultrasonic sound.
These transducers are available from electronic hobby suppliers etc. as they are often used in robot control systems.
This one was from Maplin - it has a central frequency of 40 kHz which nicely matches the FMG-3 output and cost just over 6 UK pounds.

We now have an ultrasound signal and Stu has found another inspirational way of dealing with this:
IMG_2860.JPG
This is a Bat Detector which is available from several outlets at a cost of about 90 UK Pounds.
Bats emit ultrasound pulses which are at a frequency which is too high for the human ear to detect - typically 20-108 kHz depending upon the species.
As the output from our Ultrasonic Transmitter is in the same range........... if we place the Ultrasonic Transmitter close to the microphone of the Bat Detector, it will treat the signal in the same way it would a bat call :P

The Bat Detector uses a simple heterodyne circuit - which in simple terms that even I can understand, works like this:
The detector generates a reference signal at a frequency (pitch) which can be varied by turning the dial (see the image above).
This reference signal is compared to the signal picked up by the microphone and a new signal equal to THE DIFFERENCE BETWEEN THEM is generated and output via a microphone.
So ~ if the bat (or our magnetometer) produces a signal of 60 kHz (too high for the ear to detect) and we tune the Bat Detector dial to 62 kHz then we will get a 2 kHz sound from the microphone which can be heard by our ears.
In effect, the high frequency bat calls are replicated at a lower pitch so that we can hear them; but we can do more than that.
The Bat Detector has an earphone socket and this can be used to transfer the audio output signal to a computer sound card where it can be recorded, manipulated and analysed.

Anyway, enough of the theory......... I now need to put the bits together and dee if they actually work :roll:
Last edited by grimble_cornet on Tue Jan 13, 2015 1:23 am, edited 1 time in total.
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Re: Magnetometer Project

Post by swisswalter » Thu Jan 08, 2015 9:46 pm

Hi Mike

thank you very much for the details. Please be prepared to be a warehouse to supply at least one full set of the needed stuff to switzerland asp. I do not really understand what you are doing, but it is very, very interesting
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Magnetometer Project

Post by Carbon60 » Thu Jan 08, 2015 9:53 pm

Looking good there, Mike. It's coming together.

Please send me a PM with your email address and I'll send you the Excel file I've developed to chart the data.

Cheers

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by marktownley » Thu Jan 08, 2015 9:59 pm

You've described it very clearly there Mike, I look forward to the next chapter!
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Re: Magnetometer Project

Post by Derek Klepp » Fri Jan 09, 2015 9:23 am

Excellent Mike.Stu what about telephone lines?As an aside Mike when I am outside on Summer night I often have Microbats flying through my shed and have even had them snapping insects around my head.They really are a great creature.

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Re: Magnetometer Project

Post by Carbon60 » Fri Jan 09, 2015 12:06 pm

Hi Derek,

Telephone lines shouldn't be a problem, although it is best to try to place the sensor in a spot that is furthest away from any form of magnetic interference, within reason. No need to go to the middle of the Outback! :lol:

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by grimble_cornet » Fri Jan 09, 2015 2:42 pm

OK, here we go with phase two......


Here is the FGM-3 sensor connected to one end of a 25 m length of wire:
image.jpg
It is soldered and each joint covered with a short length of heat-shrink tubing before the whole area of the pins is protected by a larger diameter length of heat-shrink. The idea is to protect the joints from short circuits and to 'bulk up' the join between the sensor and the fairly fine wires.
The cable is 9-core screened data cable which I had lying around from a previous project. The individual wires are pretty fine and I would go for a 3-core version with heavier guage wires if I was starting from scratch. This type of screened cable helps to prevent signal loss and, as the signal from the sensor is fairly weak this is quite important. I was a bit worried that the fine guage wires might reduce the voltage over 25m but we will see....... I can always replace the cable if needed.

For initial testing I am using a 'breadboard' which is just a circuit board 'look alike' which allows components to be connected temporarily before final assembly - it is the blue rectangular block in the photograph shown below:
image.jpg
The breadboard is not really needed but I had it lying around in my electronics box so decided to use it for a quick play.


In the photograph, you will see the roll of cable with the three connections from the FGM-3 sensor (+5v, ground and output) going into 3 different 'rows' on the breadboard (the holes in each row - across the narrow part of the board - are connected internally).
The battery box is then connected to two of these rows providing the +5v and ground for the sensor.
Finally, the white cable connects the two wires from the ultrasonic tranducer to the ground and output pins on the FMG-3.
It sounds complicated but really only involves making 4 connections.....just make sure that they are THE RIGHT connections!
image.jpg

That completes the wiring and if we have got it right, the FMG-3 should be sending a signal to the transducer which should now be transmitting ultrasound.


As I can't hear ultrasound........... I now need to bring the Bat Detector into play. It is positioned with its microphone close to, and in line with, the ultrasound transducer and switched on.

The moment of truth............
Turn the tuning dial from its lowest frequency upwards and..... We get a loud whistling sound at 77.6 kHz which fades and then peakes again at 84.6 kHz. Tuning upwards again, the sound fades away to nothing.



:movie YES............. WE HAVE A MAGNETOMETER :movie



If you remember...the Bat detector compares the signal it receives with a reference frequency, set on the dial, and then transmits its own signal at a frequency equal to the difference between the input and reference signals. This means that NOTHING is produced when the dial is set to the same frequency as the input BUT a signal will be produced when the dial is set above OR/AND below it. If my understanding is correct (there goes another flying bacon sandwich) then this means that the FGM-3 is sending a signal at about 81 kHz = mid way between the two sound peaks from the Bat Detector.

The next stage is to connect the output from the Bat Detector to my laptop sound card so the signal can be displayed, recorded and analysed.

Watch this space.....
.

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Re: Magnetometer Project

Post by grimble_cornet » Fri Jan 09, 2015 4:36 pm

Quick update.....

I managed to take the output from the Bat Detector headphone socket and feed it into the microphone socket on the soundcard of my old Win 7 laptop.
Opened up Spectrum Lab (more later) and played about until I got a reading on the screen:
image.jpg
The screen scrolls downwards as time passes...
The blue line is the signal from our Magnetomer.....fairly steady trace until....

I pass a small steel nail along a path parallel to the dectector and about 30cm (1 foot) away - you can see the result!

Moving the nail in an arc about 1m (3 feet) away from the detector produces a quite obvious deflection of the trace so we at least have a working metal detector!

All of this is with the Bat Detector on very low output volume and Spectrum Lab in basic display mode.

Turning the sensitivity up a bit results in more activity including several quite dramatic responses NOT caused by anything i am doing:
image.jpg
This thing is certainly very sensitive - might have to build a housing for it so that it can go outside away from central heating and magnetic fields generated by electrical appliances :oops:
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Re: Magnetometer Project

Post by marktownley » Fri Jan 09, 2015 6:23 pm

Way cool! I like it! :cool:

Look forward to reading more. I caught myself looking up the bits on the internet last night...
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Re: Magnetometer Project

Post by Carbon60 » Fri Jan 09, 2015 8:56 pm

Looking great there, Mike.

You'll find that the second (right hand) microphone on the bat detector (erm..magnetometer) is better than the left one.

Thanks for the email. I'll send you two files in return. One is a configuration file for Spectrum Lab which will set up the screen as mine with time along the horizontal axis and frequency on the vertical with sampling at 2.5 minute cadence. You can use this as a basis for your own particular colour taste etc. ;)

The second file is the Excel file to display the results (lots of number crunching to scale and filter the results). You will be able to paste the frequency/time data from a text file from Lab View for the excel file to work with.

In the meantime, here is a snapshot of one of the display configuration screens with setting used.
Configuration and display control 1.jpg
Configuration and display control 1.jpg (115.42 KiB) Viewed 2567 times
And the second.....
Configuration and display control 2.jpg
Configuration and display control 2.jpg (113.96 KiB) Viewed 2567 times
Displaying the data is one thing. You'll also need to save the data to file so that it can be manipulated in Excel. With Spectrum Lab this is easily done using the 'Export Calculated Data (Continuously) function which is selected from 'File' on the toolbar.
Export Calculated Data.jpg
Export Calculated Data.jpg (87.04 KiB) Viewed 2567 times
This gets you to the 'File Export Format' screen.
File Export Format.jpg
File Export Format.jpg (133.21 KiB) Viewed 2567 times
Click on the 'Filename and Activation' tab and you'll be able to set up a file to which data will be written (continuously at the defined cadence). Click 'Activate' and this will initiate capture.
Filename and activation.jpg
Filename and activation.jpg (139.61 KiB) Viewed 2567 times
Hopefully this will all make sense as you go through it yourself.

I'll send you the files now.

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by grimble_cornet » Fri Jan 09, 2015 10:22 pm

Great stuff Stuart :bow2

I have actually got most of this set up now after an hour working through your original instruction booklet............ data is being saved at 30 second intervals as I type :P

I will use your script to set up Spectrum Lab so that we are both using exactly the same settings as that will obviously simplify any trouble shooting in the future :lol: :roll: :lol:

Got a busy weekend so probably be a couple of days before I get around to Phase 3 - be patient :lol:
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Re: Magnetometer Project

Post by swisswalter » Sat Jan 10, 2015 7:19 am

Hi Mike and Stuart


what a great project. Congratulations to have reached phase #2. Why is the antenna 25m long ? Do you have to burry it unfolded?
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Magnetometer Project

Post by Carbon60 » Sat Jan 10, 2015 7:36 am

Hi Walter,

The 'Antenna' is actually just a connection wire to enable the sensor to be placed in a relatively remote position in Mike's garden whilst allowing it to be connected to a stable low voltage power supply and extracting the frequency signal in his house where he will keep his lap-top. All of the magnetic sensing is done by the little FGM-3 'slug' at the end of the wire.

The sensor is very temperature sensitive, so Mike will have to bury it in the garden about 0.5m below the surface or so. Clearly he has to protect it from water ingress, hence the need for a waterproof housing. All details are given in the tutorial ;)

The FGM-3 sensor is also sensitive to voltage fluctuations. It can be driven by a 6V battery supply (i.e. 4XAAs), but for a more permanent set up it is better to use a highly regulated voltage supply. The long length of connection wire to the sensor should be screened to minimise extraneous interference.

Cheers

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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Re: Magnetometer Project

Post by Carbon60 » Sat Jan 10, 2015 7:39 am

grimble_cornet wrote:Great stuff Stuart :bow2

I have actually got most of this set up now after an hour working through your original instruction booklet............ data is being saved at 30 second intervals as I type :P

I will use your script to set up Spectrum Lab so that we are both using exactly the same settings as that will obviously simplify any trouble shooting in the future :lol: :roll: :lol:

Got a busy weekend so probably be a couple of days before I get around to Phase 3 - be patient :lol:
No problem, Mike. We'll carry on when you are ready. I'll just set out the routine I use to transfer the recorded data from Spectrum Lab to Excel for you when you come back to it.

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
DMK41, Basler acA1920-155
NEQ6 Pro-mount
Fluxgate Magnetometers (1s and 150s Cadence)
More images at http://www.flickr.com/photos/solarcarbon60/

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