{"id":82,"date":"2018-12-29T19:53:45","date_gmt":"2018-12-29T19:53:45","guid":{"rendered":"http:\/\/localhost:8080\/wordpress\/?p=82"},"modified":"2018-12-31T15:32:54","modified_gmt":"2018-12-31T15:32:54","slug":"esperanzas","status":"publish","type":"post","link":"https:\/\/aprovechar.org\/?p=82","title":{"rendered":"esperanzas"},"content":{"rendered":"\n

Just what can we accomplish with this device? Here I want to compare the resolution of the sensor I have chosen to the magnitude of various magnetic anomalies to see if we can actually measure anything geophysical.<\/p>\n\n\n\n

Before I began this exercise I looked around for examples of magnetic field anomalies<\/a> seen in the field, especially associated with ore bodies. I found some excellent examples from a variety of sources, including the classic book Applied Geophysics by Telford, Geldart, and Sheriff<\/a> on my office bookshelf. It seems that over ore bodies, anomalies of between one hundred and several thousand nano Tesla are common (see the example from the paper by Gunn and Denith: Magnetic responses associated with mineral deposits<\/a>; although not surprisingly reports by Integrated Geophysics Corporation<\/a> show considerably smaller anomalies of about less than to a few nano Tesla for shallow sedimentary structures. <\/p>\n\n\n\n

So, given that we want to resolve >100 nT anomalies here is what I did.<\/p>\n\n\n\n

I began by reading the following report: Fluxgate Magnetometer by Carl Moreland<\/a> where he mentions the Speake & Co. FGM-3 sensor<\/a>, which according to Moreland has resolution of about 10 nT.<\/p>\n\n\n\n

There is also the description of home-brew magnetomteters: Practical Guidelines for building a Magnetometer by Hobbyists Part 2 by W. Bayot.<\/a><\/p>\n\n\n\n

These sensor types required more electronics development than I felt was necessary in this day and age, so after further investigation I purchased the best quality and easy to interface, but less than $100 magnetic field sensor I could find: the PNI RM3100 evaluation module.<\/a><\/p>\n\n\n\n

\"PNI
PNI RM3100 Sensor<\/strong><\/figcaption><\/figure>\n\n\n\n

This has a resolution of 13 nano Tesla, which should be sufficient to detect many mineral deposit signals. This uses magneto-inductive technology: see Magneto-Inductive Technology Overview; Andrew Leuzinger & Andrew Taylor, February, 2010)<\/a> or Slawomir Tumanski\u2019s article \u201cInduction coil sensors \u2013 a review\u201d.<\/a><\/p>\n\n\n\n

By comparison, for example, looking at Sparkfun Electronics<\/a> and Digikey Corporation<\/a> we see it is costly to obtain better than a 10 nano Tesla device. There may also be several options using magneto-resistance<\/a>, but I did not pursue these.<\/p>\n\n\n\n

For an overall comparison of resolution and cost for the easier to interface options as of January, 2015:<\/p>\n\n\n\n
Device<\/th>resolution<\/th>cost<\/th>source<\/th><\/tr><\/thead>
Honeywell HMC5883L
Breakout board<\/td>		500 nT<\/td>$15<\/td>Sparkfun<\/td><\/tr>
Freescale MAG3110
Breakout board<\/td>		100 nT<\/td>$15<\/td>Sparkfun<\/td><\/tr>
PNI RM3100
Evaluation module<\/td>		13 nT<\/td>$61<\/td>PNI Corp<\/td><\/tr>
Honeywell HMC2003
module<\/td>		4 nT<\/td>$328<\/td>Digikey<\/td><\/tr>
Honeywell HMR2300-rs232
module<\/td>		6.7 nT<\/td>$871<\/td>Digikey<\/td><\/tr><\/tbody><\/table>\n\n\n\n

Now that the tiny magnetometer is up and running here in Ecuador with the PNI RM3100, we'll see if it lives up to my dreams.<\/p>\n","protected":false},"excerpt":{"rendered":"

Just what can we accomplish with this device? Here I want to compare the resolution of the sensor I have chosen to the magnitude of various magnetic anomalies to see if we can actually measure anything geophysical. Before I began … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-82","post","type-post","status-publish","format-standard","hentry","category-tiny-magentometer-from-2014-2015"],"_links":{"self":[{"href":"https:\/\/aprovechar.org\/index.php?rest_route=\/wp\/v2\/posts\/82","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aprovechar.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aprovechar.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aprovechar.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aprovechar.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=82"}],"version-history":[{"count":3,"href":"https:\/\/aprovechar.org\/index.php?rest_route=\/wp\/v2\/posts\/82\/revisions"}],"predecessor-version":[{"id":243,"href":"https:\/\/aprovechar.org\/index.php?rest_route=\/wp\/v2\/posts\/82\/revisions\/243"}],"wp:attachment":[{"href":"https:\/\/aprovechar.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=82"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aprovechar.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=82"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aprovechar.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=82"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}