There is indeed a relationship between Teslas and Gauss, but admittedly it took some 'dusting' of the old physics texts when EN61000-4-8 (Power Frequency Magnetic Field Immunity) testing became a requirement under the new light industrial/residential immunity standard.
When a magnetic (H) field permeates a cross-sectional area of a medium, it becomes magnetic flux density (B-field). So, B equals H times the permeability of the medium. A one Ampere/meter H-field is equivalent to 1.26 microteslas. And, 1 tesla equals 10e4 gauss. And 1 oersted equals 80 A/m. The Biot-Savart Law predicts a 1 A/m magnetic (H) field at the center of a round 1 meter diameter single-turn loop carrying 1 Ampere of current. The correction factor for a square loop is 4/(1.414 x pi), or 0.9. Not exactly your everyday digital terminology! Since the size of the EUT requiring magnetic immunity testing determines loop size, I have found it convenient to build inexpensive square multi-turn loops using 3/4-inch white PVC water pipe (schedule 40, thickwall). For the lab that already has Spectrum Analyzers that tune to power frequency,a lab-quality gaussmeter is not necessary. Such custom loops are easily calibrated by placing a small calibrating loop (such as the Solar Electronics 7334-1) at the geometric center of the immunity test loop. Calibration curves accompanying the small calibration loops relate dB microvolts per meter to dB picoTeslas. The magnetic immunity test is only required to be carried out if the EUT contains devices susceptible to magnetic fields. Like Hall Effect devices, electron beams (CRT's), sensitive analog circuits, etc. The Product Family standard for professional audio requires that the test be performed not only at power frequency, but swept up into the kHz range. Regards, Jim Ericson --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
