Not wanting to deprive Rob, Baz or Pete of the opportunity to sell you
one of their very excellent standards but as a quick field check you can
use a metal filing cabinet door (~1mm steel) or an SI standard
Landcruiser door panel. My two SM30s return a number between 200 and 250
x 10-3 SI on both surfaces. Clearly not the correct answer but a
reflection of ~1mm thick magnetic material in a 10cm deep halfspace.
Different types of meters will vary - depending on their search depth.
I did have the nulling order right the first time. After 15 years of
using the SM30 others reverse has become my normal so without it in my
hand I had to think, something best done after breakfast.;-)
I'd argue that a hand held mag sus meter will not be effected by
remanence though Baz. It may not give you the susceptibility you need to
model the body (if you ignore remanence in your modelling) but the
presence or otherwise of remanence does not change susceptibility and
will not impact on a hand held mag sus meter reading. I do agree that it
is rare to get negatives though. Having said that I've seen pages of
them when people have not been using the meter correctly.
Cheers
Kim
On 13/8/20 8:55 am, Barry Bourne via SEGMIN wrote:
Signature file
Hi Jon/All,
Agree on most of the comments.
You can get negatives from remanence/conductivity. Usually pyrrhotite
is present. I would point out though this is extremely rare.
Terra Petrophysics have magnetic susceptibility reference samples for
A$200 + p/h (set of 3 low, medium and high A$500). Good to have
stored with your instruments as an easy check.
Cheers
Barry
*Barry Bourne*
Principal Consultant
Unit 5, 51 Forsyth Street, O’Connor WA 6163
*(M)*+61 409 493 485 *| (E)* [email protected]
<mailto:[email protected]>
*(Web)*www.terrapetrophysics.com.au <http://www.terrapetrophysics.com.au>
*From:*SEGMIN <[email protected]> *On Behalf Of *Kim
Frankcombe via SEGMIN
*Sent:* Thursday, 13 August 2020 8:10 AM
*To:* [email protected]
*Cc:* Kim Frankcombe <[email protected]>
*Subject:* Re: [SEGMIN] Mag Susc SM30 problems
I may have that nulling process A-about - I don't have mine sitting
here and its been a while. Whichever - it is the opposite way you'd do
it with other meters. I recall that for one of the modes I never use
that you null as per "normal" but for the others you null in reverse.
Cheers
Kim
On 13/8/20 7:23 am, Kim Frankcombe via SEGMIN wrote:
Jon
Negatives typically imply a conductive sample. If you are
measuring directly on core in metal core trays or even on non
metallic core trays lying on metal racks you can get negatives. I
always lift the core and measure it in the air.
The other trap for non manual reading beginners is that the SM30
nulls in reverse to other instruments i.e normally you would null
in air then take a reading, with the SM30 on settings 1 and 6 you
take a reading then null. If you are doing it in reverse you will
get negative readings.
Cheers
Kim
On 13/8/20 1:43 am, Benoit Tournerie via SEGMIN wrote:
To follow up on Madjid comment,
See Table 2 on https://www.publish.csiro.au/pv/pdf/pvv2016n184p41
A comparison of magnetic susceptibility meters using samples
from the Thompson Nickel Belt, Canada
Deng Ngang Deng and Richard S Smith
-----
Benoît Tournerie, /P.Geo., D.Sc./
*From:*SEGMIN <[email protected]>
<mailto:[email protected]> *On Behalf Of
*Madjid Chemam via SEGMIN
*Sent:* Wednesday, August 12, 2020 13:24
*To:* [email protected] <mailto:[email protected]>
*Cc:* Madjid Chemam <[email protected]>
<mailto:[email protected]>
*Subject:* Re: [SEGMIN] Mag Susc SM30 problems
Hi Jon,
You can see negative magnetic susceptibilities on massive
pyrrhotite samples due to diamagnetism.
Regards
image002
*Madjid Chemam, P.Geo., **M.Sc.A./MASc*
*/Géophysicien sénior / Senior Geophysicist/*
*/Abitibi Géophysique inc./*
*_____________________________________*
*tel.: 819 874 8800 #210 fax: 819 874 8801*
*1746, ch. Sullivan, Val-d’Or (Québec) CANADA J9P 7H1*
**
*www.ageophysics.com <http://www.ageophysics.com/>*
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*De :*SEGMIN <[email protected]
<mailto:[email protected]>> *De la part de* Jon
Woodhead via SEGMIN
*Envoyé :* August 12, 2020 12:42 PM
*À :* [email protected] <mailto:[email protected]>
*Cc :* [email protected] <mailto:[email protected]>
*Objet :* [SEGMIN] Mag Susc SM30 problems
Hi All,
Wondering if anyone has some advice for a client that seems to
be getting a large amount of _negative readings_ on the SM30
mag susc meter.
I simple case of user error or something (even) more serious?
Thanks
Jon
Jon Woodhead, PhD
JAW Consulting LLC
Golden, Colorado
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Senior Consulting Geophysicist
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PO Box 1191, Wangara, WA 6947 AUSTRALIA
Unit 6,10 O’Connor Way, Wangara, WA 6065, Australia
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