http://ie.mt.com/eur/en/home/products/ProcessAnalytics/Cond_family_browse/level_4_Conductivity_Premium_Inductive_Line.html
http://en.wikipedia.org/wiki/Eddy_current
http://www.solumetrix.co.uk/sensors.html
http://www.google.com/patents/US20120326711
https://www.honeywellprocess.com/en-US/explore/products/instrumentation/analytical-instruments-and-sensors/default/Pages/5000-tc-toroidal-conductivity-sensor.aspx
http://www.vl-pc.com/default/index.cfm/meters-and-accessories/knick-products/knick-sensors-including-memosens-and-fittings/knick-conductivity-sensors/se-656-electrodeless-conductivity-sensor
http://www2.emersonprocess.com/siteadmincenter/PM%20Rosemount%20Analytical%20Documents/Liq_ADS_43-018.pdf
https://estore.industrialcontrolsonline.com/products/MODEL/HONEYWELL-5000TC-SERIES.aspx
http://www.technocontrol.gr/products.php?show_category=5
