The calibration of the inductive coil is specified in the IEC 61000-4-8 standard. Place a mag field sensor at the coil center and adjust the drive current for the desired H-Field. A coil factor (CF) is defined in the standard: CF = H/I, therefore H = (CF)(I) or I = H/CF Since CF is constant, plug in the desired H-Field and calculate the required drive current I.
The current required to achieve a desired H-Field will be a function of the number of wire loops within the inductive coil. More loops means less drive current and vice versa. Additionally only a portion of the coil interior area is useable for immersion of the EUT within the H-Field (called the Field Distribution in the standard), the details are specified in the standard. Therefore coil size will depend on the EUT physical dimension. The hula-hoop mag field inductive coil that I built 20 years ago was only good for small EUT's. It was temporary to get us started, we eventually switched to a more professional looking setup (although the hula-hoop method met the standard and worked fine). Manny Barron Sr. EMC Engineer -----Original Message----- From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] Sent: Tuesday, June 21, 2016 9:28 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Magnetic Field at 400 A/m But how to calibrate such a thing, to know how much magnetizing force is really being applied to the DUT ? Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric From: Manny Barron [mailto:mbar...@integrity.com] Sent: Monday, June 20, 2016 7:54 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Magnetic Field at 400 A/m Back in 1996 when I managed a 3rd party EMC test lab and when the IEC 1000-4-8 test became mandatory, I built my first magnetic field test setup using a "hula hoop" from Toys-R-Us. I wound the appropriate amount of insulated wire loops inside it, and added an appropriate power supply/transformer and some low resistance high wattage resistors. It worked great for small products and the 3 or 10 A/m test levels. Today there are more aesthetically appealing test setups available from various suppliers. Manny Barron Sr. EMC Engineer From: Ed Price [mailto:edpr...@cox.net] Sent: Monday, June 20, 2016 7:01 PM To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Magnetic Field at 400 A/m Grace: I used to regularly test equipment to MIL-STD-1399, which had a DC magnetic field strength exposure requirement of 20 Oersteds, applied for 60 seconds. Since 1 Oersted is about 79.5 Amps/meter, that was equivalent to a 1600 Amp/meter field exposure. I did that with a Sorensen 50 ADC power supply, a 0.001 Ohm sense resistor, a DMM and a custom solenoid coil. The coil was wound with 163 turns of #12 solid wire, with a coil length of 711mm and a diameter of 590mm. This was adequate to expose a several unit high 19” rack-mount EUT. FYI, this antenna had an “antenna factor” of 2.217 Oersteds/Amp or 175.8 Amps/meter per DC applied Amp, with about 1.6 Ohms resistance. I built the solenoid coil using a “hazardous chemical disposal carboy” (think big strong plastic garbage can) with a cheap Harbor Freight appliance dolly bolted to one end. (Not only does this make the antenna easy to move, but it also greatly aids you winding that 1000 feet of #12 wire onto the carboy during several hours of Zen meditation.) Of course, if your EUT is smaller, then you don’t need such a large solenoid; I have a spreadsheet describing the design and performance characteristics of six solenoid coils I have built over the years. If anyone is interested, I have a description of the coil and the spreadsheet which I can send off-list. Ed Price WB6WSN Chula Vista, CA USA 1961 Amphicar 770 2001 Fleetwood Storm 31W 2008 Ford Explorer From: Grace Lin [mailto:graceli...@gmail.com] Sent: Monday, June 20, 2016 4:18 PM To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Magnetic Field at 400 A/m Dear Members, Does anyone know which standard requires to have magnetic field evaluated at 400 A/m? Is there any commercial available instrument (loop) for the purpose? Thank you very much for your time and I look forward to hearing from you. Best regards, Grace Lin - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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