Dear Mark, I have simulated the case with two thick Ni rings (D=5cm and D=2 cm ) placed 5 cm away from the coil. The ring wire thickness is 1 cm. Please see the pictures attached. The same analysis was carried out for AC, 50 Hz. The current induced in the inner ring is 640 A, the current induced in the outer ring is 1400 A. There are generally two ways the rings affect the magnetic field: * in DC, the ferromagnetic rings pull the magnetic field away from the center so we can see local minimum * in AC in addition to DC effect the eddy currents in the ring produce magnetic flux that is directed opposite to the flux produced by the coil. So we have local minimum. Since the frequency is low the induced currents are low: to compare with - the coil carries 707' kA*turns (500 times the ring current). I can switch off inner or outer ring - the field distortion effect will be less prominent. So I have not run this analysis. I can move the rings 4 to 6 cm away - but that will not change the principles above. Please let me know if I should run these tests. Time spent: 1.5 hours. Best regards, Alex ----- Original Message ----- From: "Mark Arokiaraj" To: "Vladimir at QuickField Support" Cc: Sent: Wed, 5 Sep 2018 09:04:00 +0530 Subject: Re: Strings or mesh Dear Alex, I am understanding how the magnetic field is distorting. Now we will try with 5cm diameter and 1cm thickness and if it works another ring inside 2 cm diameter and I cm thick. Also A/C or D/C variation we can see with this 5cm diameter and 1cm thickness. If we can give electric current to the rings A/c or D//C we will see what happens later. Another technique could be vibration or movement of the rings if it changes. This could induce time variation. We can see later. Also, we can move parametrically the distance rings from the magnet to 4cm and 6 cm if magnetic distortion changes. with regards, Mark