Ansi c63. 19 -2a -2007 Revision of
Download 1 Mb.
|
- Navigate this page:
- D.7Frequency generator
- D.9Helmholtz calibration coils
- D.10Probe, near-field, E-field
- D.11Probe, near-field, magnetic field
- D.12RF cables
- D.14RF power amplifier
D.6Directional coupler
D.7Frequency generator
D.8Hearing aid probe coil(In accordance with FCC Part 68 and IEEE Std 1027)
Table D.10—Hearing aid probe coil limits
Figure D.21—Typical hearing aid probe coil dimensions D.9Helmholtz calibration coilsRefer to D.9.1, Figure D.12, and Figure D.13.
D.9.1Helmholtz coil magnetic field generationHelmholtz coils consist of a pair of identical coils wound in a series-aiding fashion, coaxially aligned and spaced a distance apart that is equal to their radius (see Annex F). The magnetic field at the center of such a pair of coils is axially directed with a strength given by the following equation: 
where
Hc is the magnetic field strength in amperes per meter N is the number of turns per coil I is the current in amperes r is the coil radius in meters The previous equation assumes that all the turns on each coil can be considered to lie in the same place and have the same radius. In practice this means that the diameter of the wire bundle is much less than the diameter of the coil. The coil parameters are such that the magnetic field strength is numerically equal to 100 times the current flowing through the coils. Thus, if a 100 Ω resistor is used to sense the current flow, the magnetic field strength is numerically equal to the voltage across this sensing resistor. Nonmetallic materials should be used to construct the coil forms, base, and any supporting structure for locating probe coils that are to be calibrated. The method shown in this annex of interconnecting the coils and bringing out the leads to binding posts on the end of the base minimizes any disturbing effects on the desired magnetic field. 
NOTE—R = 143 mm and N = 20 turns, AWG no. 24 enameled magnet wire, per coil. Figure D.22—Helmholtz coil diagram 
Figure D.23—Helmholtz coil circuit D.10Probe, near-field, E-fieldThe probe and its associated cables shall not perturb the field by more than 1 dB from the measured quantity. Normally this requires probes of diameter less than 10 mm that are connected to the measurement instrumentation through high-resistance or non-conductive lines. The probes shall be calibrated to a measurement uncertainty of no worse than ± 2 dB. Probe calibration in accordance with IEEE Std 1309-2005 is discussed in C.3. D.11Probe, near-field, magnetic fieldThe probe and its associated cables shall not perturb the field by more than 1 dB from the measured quantity. Normally this requires probes of diameter less than 10 mm that are connected to the measurement instrumentation through high-resistance or non-conductive lines. The probes shall be calibrated to a measurement uncertainty of no worse than ± 2 dB. Probe calibration in accordance with IEEE Std 1309-2005 is discussed in C.3. D.12RF cables
D.13RF communications test setA base station simulator or other means by which the WD may be configured in the required test conditions. D.14RF power amplifier
Directory: documents documents -> Concept stage documents -> Concept stage documents -> The great global switch-off documents -> Nonprofit grant application documents -> The Truth about the Rwandan Genocide documents -> Annual InStructional unit plan documents -> Chaos equipment included Download 1 Mb. Share with your friends:
|