Fluxgate Magnetometer

		Quote:			Posted by epitopios
	GoldDigger1950 First of all I Τhank you for your reply and justified by my ignorance in these matters, Second , could you suggest me any medioum product i can make so i can have underground image ? something familiar maybe in the forum or something else ? I accept any suggestions friendly epitopios and for every body here , have a nice summer

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In the progress of purchasing and building FGM 3 type gradiometer but see that some state that the gradient sensitivity will not be better than 100 nT. Any comments?

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epitopios;
Hi, I dont want to get your hopes up, but I thought I should tell you my solution, for something similar.... but it is NOT available as a kit.

You dont say much about the logger and I cant seem to find it at EPE (Im missing something?) does it log serially or parallel data? Can you key log-on-demand, for point logging?

If it is a parallel logger, you  can make an ADC interface, which takes the analog (voltage) data and converts it to parallel digital. If it is serial, there are serial ADCs available. In my case, I designed an ADC (the old, simple ADC0801) so that the ADC cycle was keyed by a wheel )to get multiples of 2m....) when the ADC cycle finished, it latched the data into a transparent octal latch:- the latch pulse has to be inverted, for the latch IC,  so it is positive logic. This pulse also acts as a strobe. The data, on the latch, is keyed by the logger, once per cycle. Basically simple.... and no PIC processors. IF your logger works for point-to-point.

Since I didnt have a nice logger and wanted GPS data, I used a simple USART to convert the parallel, digital data, to serial and modulated an AFSK circuit. After each cycle, the GPS  also sends (cleaned up) serial data to the AFSK unit. I could transmit this to a base computer, but chose to save it, as audio tones, on a digital sound recorder.

I DONT recommend this solution!  but you could use a serial ADC and get the data on a serial logger. Ive got some stuff on some OLD printer port loggers but could never find a program to run them. I could write one but I am limted to Basic and its full of peek and pokes, still, if you are doing  points as opposed to continuous, it would be fast enough (GoldDigger1950 doesnt agree, of course )

A PIC processor, to just grab the data, from the ADC, and stick it on an SD card would be simple... the PIC is just an intermediary, and only has to be as fast as the bytes of data arrive, data content would NOT be processed, in any way, just saved. Afterwards, stick the SD card into your computer and save/process the data any way you want.

I dont know if that helps or drives you crazy? (NO-BURN-OF-THREAD)

Brian AKA goldigger (a fish HAS to swim upstream!)

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GoldiDigger1950;

Something like that I,ll bet!

I used to use a C64, it had a disk programme to turn your basic into what they called P-code (NOT Roscoe P Coltrane, just Pseudo code) With the XT onward, you could assemble a Basic programme into an EXE.... same idea.

So, it also works with PIC Basic. But still, to cram data, handed to it, into an SD card, it doesnt have to be blazing fast. Its the kind of repetitive task that would drive an intelligent PIC IC, thoroughly MAD (cheeky tongue in cheek. )

Brian AKA goldigger ( )

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epitopios;

I do not know if you read my other post to you, but I will try again, with this one. I have noticed that Cornelius can be too busy to answer posts, sometimes and when he does, it might be too brief.

A logger, for your purpose, would probably  be a serial logger and would use a chip to control read and write to serial memory chip or SD card, thus the software (called firm ware, in this case) would be pre-programmed into the micro-controller that performs the read and write. All you have to do is push a button for 'log,' or 'download,' or stop, or on/off.

If you can find a serial logger, with a very large memory, it is already programmed, and you will only have to worry about keeping the signal to be logged, in the right voltage range, for the logger. Also a 2 gigabyte SD card holds a lot of logging and you can now get 8 gigabyte SD cards. Example: if each point logged takes 100 bytes, then a 2 gig SD card will log about 2,560,000 points!

You might do the whole of Greece, with an 8 gig SD!! 

For example, if the logger has a 5 v maximum input, you most likely want to feed it 2.5 volts, so the signal can vary, from zero volts, to 5 volts.... this gives a + and - capability. But, if the detector/magnetometer output is zero until an anomaly occurs, then you have to limit it to + 5 v on peaks as it will be 0v the rest of the time (0v to 5 v range.)

If you can, check out the 'HOBO' loggers, I know they are serial, but I do not know if you can set them for continuous logging, logging on demand, or interval logging. I do know they are lower priced than some, and have single channel to multiple channel logging.

They are small and simple. If you get one, read all the paperwork, if your English is so so, get someone who is fluent in English, to read it, also check it out, on the internet, if you can..... be sure, before you buy.

Come to think of it I am going to the internet to check them out, myself.... good plan! Thank you for telling me! 

Bear in mind, what ever you log, you will have to download to a computer file, then to work it into something meaningful, you have to have the right software, usually Excel, to lay the readings out, on a map or something, so you can see the results of the logged data. Excel has a learning curve, so if you know a computer Geek that uses Excel, then you are OK.

If you can make this work for you, I  would suggest it would fit your needs, fairly well. (How do I know your needs? You told me.) 

goldigger




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