Magnetic Susceptibility Meter

[Ferric Toes]

I need a schematic to build a susceptibility meter, or purchase a commercial unit at reasonable price. Preferably a two frequency one.

Eric Foster

[99thpercentile]

A dual frequency field sensor doesn't exist. Check some articles by Tabbaugh or Benech for research into field sensors that can measure the magnetic viscosity of soil (the frequency dependence that you could calculate from dual frequencies). You could build a sensor as most of them are simply resonant coils. The coils is drive by an oscillator and a measurement is made in the air where the susceptibility is assumed to be zero. Next a measurement is made on the ground surface and the frequency of oscillation is changed by the presence of the magnetic material in the vicinity of the coil. The change in frequency from ground to air is proportional to the magnetic susceptibility. There are a number of papers on most of this sensors. Download a copy of Environmental Magnetism Using the Bartington MS2 System by John Dearing from the Bartington website. Here are the instruments that are on the market that can measure in-situ magnetic susceptibility.

Bartington MS2 system (Sensors D, F and H measure in-situ) ~$10K
I use all of these on a regular basis as well as the laboratory sensors (B, C, etc). This is the most popular susceptibility meter in the world.

ZH Instruments SM-30 ~$1500
This sensor is the size of a pack of cigarettes and is easy to use. I have used it a lot as well as the SM-100 lab sensor.

GF Instruments SM-20
This is identical to the older ZH Instruments SM-20.

Fugro KT-9 ~$1500
Never used it.

Geonics EM38B ~$14K
This is the only slingram instrument in this list and is specifically designed for shallow soil conductivity mapping. It can also be used for point susceptibility measurements.

Ryan

[Morris_jo]

Hello 99thpercentile,

I think you have a good experience with geophysic instruments, they are alot of manufacutures like: GSSI, Geonics, Geometrics, Geophex .....etc .

What do you think of SuperSting R8/IP ?

http://www.agiusa.com/supersting.shtml



Best regrads

[99thpercentile]

It's a good instrument. Mats has been building resistivity systems for a long time since he worked at ABEM. We have a SuperSting R8 at work with 112 electrodes and all of the accessories. It was about $100K all inclusive. You can rent their systems or buy a smaller setup. You have the choice of using their in-house inversion package or using RES2DINV. That's my two cents, if you have more questions let me know. I've been to the AGI office three or four times and have taken all of thier training courses. Markus, Mats' son who now runs the new AGI office in Spain, was an undergraduate at CSM when I did my MS.

Ryan

[Geophyz]

I need a schematic to build a susceptibility meter, or purchase a commercial unit at reasonable price. Preferably a two frequency one.

Eric Foster

Eric,
The lowest cost MS meter I know of is manufactured by an agricultural supply company called Pike Agri-Lab Supply http://www.pikeagri.com/ . It is marketed as the "PCSM meter". It measures in the old cgs system. Price is US $425. I believe they manufacture this meter 'in house'. It is single frequency. Uses standard film canisters for soil sample.

http://pikeagri.com/index.php?page=s...mart&Itemid=39

[99thpercentile]

That's a sensor that I've never seen before. It is actually a lab sensor that requires a soil sample to be collected and then put into the measurement chamber. I have seen the book by the author before, I don't really do agriculture so I don't know the quality of the book. It seems a little quacky to me, but I don't know enough to make a qualified opinion. I just did a Google search on the theories relating paramagnetism to plant growth and the concensus is that it doesn't correlate. The instrument seems interesting, it seems to be a resonant coil device which means that a coil of wire is wound around an air core. The coil is driven with a known frequency and when the core is empty it should resonant at that frequency. When something other than air is put it the coil and the frequency generator is turned on, the resonant frequency will be slightly different than the driving frequency. The difference in frequency is proportional to the magnetic susceptibility. The precision of a resonant coil system is a function of how accurately the frequency change can be measured.

This system is about two orders of magnitude less sensitive than most sensors on the market. So it depends what you want to do with it whether that makes a difference to you.

[Geophyz]

This system is about two orders of magnitude less sensitive than most sensors on the market. So it depends what you want to do with it whether that makes a difference to you.

actually, K= 1 x 10-6 cgs. This is the same resolution as the Bartington MS2 (page 13 of the MS2 manual) minus the extra decimal space (0.1 mode only). The PCSM instrument has a better reported accuracy than the old Scintrex MS meters. It is designed to be used in the field on battery power with standard film canisters. Just scoop up the soil sample into the vial, and take the measurement. X could be determined back at the lab if the mass of the sample was known.

As for the theory behind this instruments use in agriculture...sounds like quackery to me. But heh, if the instrument can measure MS for $425, it sounds like a nice deal. I have never seen a cheaper MS meter. I own two Bartington MS2's and various coils (one for field use and one set up for lab use). I love the Bartington's...but I can appreciate the PCSM becuase of it's price/value. But I must admit that I have never used the PCSM, but I have spoken to the manufacturer.

I have spoken with the Pike Agri-supply people about this meter and they are very nice. They spent 1/2 hour with me on the phone...and were SUPER. I believe they even mentioned that they would consider making a dual-freq version if demand required it. So it would not hurt to ask.

[99thpercentile]

I wasn't saying that it may not be a decent value, it just depends on what you want to do with it. I like that it uses film canisters, which my two newest sensors use as well. My biggest complaint with the Bartington MS2B is the sample jars which can become expensive. I have a complete Bartington MS2 system with all of the coils for both field and lab use. I also have a core track logger that any of the MS2C sensors can connect to to automatically log cores. I recently purchased two instruments from ZH Instruments, the SM-30 for field use and the the SM-100 for laboratory use. I have been funding the development of a new sensor, the MAGNASAT, for lab use by Queensland Magnetic Research. It uses film canisters for sample holders and can measure over a wide frequency range (10 Hz to 100 kHz).

I have also used a number of other sensors at the University of Minnesota's Institute for Rock Magnetism.
Quantum Designs MPMS ($500,000 plus monthly liquid nitrogen costs)
Lakeshore Cryotronics 7100 (out of production)
AGICO KLY-2
Marvington (modified Bartington MS2B which is more accurate and sensitive)

The PCSM might be a great value, but it all depends on what your end goal is. If you want to map a site, that type of sensor is quite slow. If you are interested a limited number of sample just to characterize a site it might be great. In my experience field measurements are more efficient with a field sensor. What doesn't exist that I want a may have build is a sensor similar to the MS2D the makes measurements at two frequencies simultaneously with logging capabilities and GPS recording capabilities.

[Geophyz]

I like that it uses film canisters, which my two newest sensors use as well. My biggest complaint with the Bartington MS2B is the sample jars which can become expensive.

Yeah, I have same complaint. I use the 1" 10cc cylinder pots. Cost ~$2.50 a piece, so it adds up fast. A film canister can fit into the MSB and I know many people who use this method when they correct for the difference in mass. I use the standard 10cc pots myself. Many other instruments also use the 10cc pots (same diameter as a 1" core), but it is nice to hear that film canisters are becoming more accepted. My older Bison MS meter used film canisters...but I tossed it in the trash a few years back because the battery was impossible to find. Should have kept it around...I could have just given it to Eric Foster for his research!

I have been funding the development of a new sensor, the MAGNASAT, for lab use by Queensland Magnetic Research. It uses film canisters for sample holders and can measure over a wide frequency range (10 Hz to 100 kHz).

That sounds like a great project. The wide freq. range will be nice for viscosity studies. Is this a very expensive instrument?

Marvington (modified Bartington MS2B which is more accurate and sensitive)

An MS2B modification? I need to know more. Can you supply me with more info?

What doesn't exist that I want a may have build is a sensor similar to the MS2D the makes measurements at two frequencies simultaneously with logging capabilities and GPS recording capabilities.

I already know somebody who has developed this into the prototype stage. (Contact me through the board, I will give you details). But I really don't see the benefit of having dual freq. capabilities when dealing with K in the field. How accurate will the freq. dependence be if one can not account for the mass of the sample? Seems like the freq. dependence will be relative and not absolute because the mass will be unknown from one location to the next. Might be useful, but it also might be difficult to compare readings across a wide geologic area. Tell me more about what you are thinking about the potential applications.

[Ferric Toes]

Many thanks to all, for the replies to my original questions. The background to this is that I design pulse induction metal detectors, some of which are used in adverse soil conditions. Recently I have designed a detector for use in Australia where the ground gives a very strong response in some areas, unless some form of ground cancelling electronics is incorporated. The ground response is caused by a concentration of superparamagnetic particles that exhibit a magnetic lag, or viscosity. I am trying to do some measurements on rock and soil samples to determine how Australian ground stands in relation to samples from other areas. I recently adapted an inductance meter to give an indication of susceptibility, by the change in inductance of a coil when a sample is present. The meter I used runs at 1kHz. The Australian sample gave a considerable change in reading, exceeded only by a lump of magnetite rich ore from an iron mine in Sweden. However, the magnetite does not give a signal on a PI metal detector because it does not have particles that exhibit superparamagnetism. That is why at least a two frequency device would be more relevant, since it would indicate any frequency dependent susceptibility, which give rise to the magnetic lag.

You can find schematics for most electronic devices, but for susceptibility meters seem to be almost non existent and, I was hoping to avoid the high cost of a new Bartington unit. However, Bartington Instruments are only 20 miles from my workshops and they said they could run some tests for me, although I would prefer something in house if possible.

Eric.

[99thpercentile]

If you're in Australia, then Minelabs is dominating the market for metal detectors that can remove the effects of magnetically viscous soils. I'm actually working with a research at CSIRO on designing my new lab sensor. For your interests a single sensor instrument isn't much use. The diffuculty with multifrequency instruments is stability and field strength. To do a valid calculation of magnetic viscosity you need to know that the field strength is the same at both frequencies. Magnetic susceptibility is dependent on field strength, temperature and frequency.

Does Bartington have an Australian office or are you actually located in the UK?

[Ferric Toes]

Hi Ryan,

I am located in Oxford, UK. I guess you could say that I am a competitor to Minelab as I have a detector that will perform smoothly in areas where the ground still generates a lot of noise on their gold detectors. However, my manufacturing facility is much more limited than theirs and I now concentrate more on design and consultancy for other detector companies.

I first developed a ground cancelling pulse induction detector back in 1983 and it was fine in most places other than Australia, where the amplitude of the signal tended to drive parts of the receiver circuit beyond their linear mode of operation, resulting in distortion of the viscous decay curve, and subsequent problems with the balancing circuit. The present detector has these problems addressed.

My first encounter with magnetic viscosity was in the mid 1960's when I was developing electronic survey equipment at the Research Laboratory for Archaeology, Oxford. There we often made use of the effect in archaeological surveys for the location of buried pits and postholes. This was an early PI unit that was often used in conjunction with a proton magnetometer.

Eric.

[99thpercentile]

I do have a couple of journal articles on building magnetic susceptibility meters. I'll look for them. Eric, I would love to talk to you some more about this. Send me an email.

Ryan

[JC1]

Searching for Water on Mars

Hi Eric,

Maybe Help? Who knows.

Remember John Corbyn {not me} article.

http://mars.mines.edu/magsus/custLCR.htm

[99thpercentile]

That system is in Gary Olhoeft's lab and was used by Dave Stillman for his PhD work. They took the loop from a Sapphire instruments magnetic susceptibility meter and hooked it up to an LCR meter. It works okay over a limited frequency range. Dave was an undergraduate when I did my MS at Mines. I worked with Gary Olhoeft for a while when working on my MS. I am currently at Mines working on my PhD with Yaoguo Li.

Ryan