From: lfresea...@aol.com [mailto:lfresea...@aol.com] Sent: Tuesday, September 23, 2003 4:50 AM To: emc-p...@ieee.org Subject: Magnetoic field test in DO-160
Hi all, I'm looking into the best way to perform the magnetic field from equipment test in DO-160. I'm currently using a compass, but has any one got a better idea? If I have to stick with a compass, has anyone go a preferred Vendor/model? Thanks, Derek N. Walton Owner, L F Research EMI Design and Test Facility Poplar Grove, IL 61065 Derek: I assume that you are referring to Section 15 (Magnetic Effect) of DO-160. I always wondered about how RTCA expected somebody to read a 1 degree deviation on a mechanical compass! I started a spare-time project on that last year, but the program evaporated, and I set it aside. But here's the idea. I bought a couple of Honeywell HMC-1002 2-axis magnetic sensors (SOIC surface mount devices, so I soldered them to a pair of 0.1" SIP Surfboards). The Honeywell devices (about $20 each from Newark) are magnetoresistive devices with a sensing range of -2 Gauss to + 2 Gauss, a maximum field of 10,000 Gauss, and a resolution of 27 microGauss. You feed the chip with 5 VDC and get a linear output of 5 mV/Gauss. With a modest external op amp, you can get 2.5 V/Gauss. (I hadn't decided whether to read this DC voltage directly, or to use a voltage-to-frequency converter and use this to modulate an LED for a fiberoptic link.) I think Honeywell offers chips with built-in serial converters that give you an RS-232 output. The idea is to read the two magnetic field strengths, and calculate a trigonometric solution that is equivalent to the standard's allowable "degrees of compass deviation". See the Honeywell web site: http://www.magneticsensors.com they have a bunch of application notes and suggested circuits for using magnetoresistive bridge devices. Regards, Ed Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty
