Conformity Magazine - June 2008 - (Page 58)

Definitions/Equations Air Core Inductance - Lo (H) The inductance that would be measured if the core had unity permeability and the flux distribution remained unaltered. General formula Lo= 4π N2 10-9 (H) C1 Toroidal Lo = .0461 N2 log10 (OD/ID) Ht 10-8 (H) Dimensions in mm’s Attenuation - A (dB) The decrease in signal magnitude in transmission from one point to another. It is a scalar ratio of the input magnitude to the output magnitude in decibels. Core Constant - C1 (cm-1) The summation of the magnetic path lengths of each section of a magnetic circuit divided by the corresponding magnetic area of the same section. Core Constant - C2 (cm-3) The summation of the magnetic path lengths of each section of a magnetic circuit divided by the square of the corresponding magnetic area of the same section. Effective Dimensions of a Magnetic Circuit Area Ae (cm2), Path Length le (cm) and Volume Ve (cm3) For a magnetic core of given geometry, the magnetic path length, the crosssectional area and the volume that a hypothetical toroidal core of the same material properties should possess to be the magnetic equivalent to the given core. Field Strength - H (oersted) The parameter characterizing the amplitude of the field strength. H = .4 π NI/le (oersted) Flux Density - B (gauss) The corresponding parameter for the induced magnetic field in a area perpendicular to the flux path. Impedance - Z (ohm) The impedance of a ferrite may be expressed in terms of its complex permeability. Z = j ωLs + Rs = j ωLo(µs' – j µs") (ohm) Loss Tangent - tan δ The loss tangent of the ferrite is equal to the reciprocal of the Q of the circuit. Loss Factor - tan δ/µi The phase displacement between the fundamental components of the flux density and the field strength divided by the initial permeability. Phase Angle - Φ The phase shift between the applied voltage and current in a inductive device. Permeability - µ The permeability obtained from the ratio of the flux density and the applied alternating field strength is: Amplitude Permeability, µa - when stated values of flux density, are greater than that used for initial permeability. Effective Permeability, µe - when a magnetic circuit is constructed with an airgap or airgaps, and then the permeability is that of a hypothetical homogeneous material which would provide the same reluctance. Incremental Permeability, µ∆ - when a static field is superimposed. Initial Permeability, µi - when the flux density is kept below 10 gauss. 58 Conformity JUnE 2008 Figure 17 Figure 18 Figure 19 Figure 20

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Conformity - June 2008 Contents Editor's Note 700 MHz Auction Raises a Record $20 Billion FCC Modifies PCS and AWS Power Limit Rules for Broadband Wireless Commission Designates Spectrum Test Bed FCC Releases Report on Wireless Competition Commission Proposes $5 Million Fine for Slamming Using EDX for Non-Destructive Detection of Lead in Consumer Products ESD Open Forum Challenges in Testing - Improving Election Security and Accuracy Part 1 Challenges in Testing - Human Body Model: The Hidden Challenges High-Speed Signal Integrity Considerations for ESD Components Focus On...EMC Components Buyer's Guide FCC Levies $2.6 Million Fine for Junk Faxes FDA Updates Guidance on its Product Review Process EU Issues Updated Energy Star Regulations EU Repeals Directive on Veterinary Electro-Medical Equipment New Product Announcements Updated Standards List for the EU's PPE Directive CPSC Announces New Effort to Keep Out Hazardous Products CPSC Actions in the News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity - June 2008

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