gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080707-1951 EST
Post #1 never mentioned a Gauss meter. EMF was not clearly defined. It now appears for this and may be many other threads EMF means magnetic field flux density.
A multiturn coil as a Gauss meter will have an output voltage proportional to frequency. So unseparated harmonics produce a greater effect than the fundamental. It is sensitive to frequency because the induced voltage is proportional to the rate of change of flux. The coil is bandwidth limited at some point from shunt capacitance.
A Hall device is is insensitive to frequency because it directly measures flux density. It also will rolloff after some high frequency limit.
See
http://www.euro-emc.co.uk/datasheets/Magnetic/EMF Fundamentals.pdf
for some discussion on assumptions on the effect of AC magnetic fields on humans. The calculations are based on the assumed characteristics of a human in a varying magnetic field. See page 5 and the table on magnetic flux density and assumed induced voltage. Note these are the induced voltages around a waist of 1 meter and are in the millivolt range. Also note the current desnities per sq-meter, rather low current per sq-cm. At 5000 mG their density is about 0.14 microA/sq-cm.
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Post #1 never mentioned a Gauss meter. EMF was not clearly defined. It now appears for this and may be many other threads EMF means magnetic field flux density.
A multiturn coil as a Gauss meter will have an output voltage proportional to frequency. So unseparated harmonics produce a greater effect than the fundamental. It is sensitive to frequency because the induced voltage is proportional to the rate of change of flux. The coil is bandwidth limited at some point from shunt capacitance.
A Hall device is is insensitive to frequency because it directly measures flux density. It also will rolloff after some high frequency limit.
See
http://www.euro-emc.co.uk/datasheets/Magnetic/EMF Fundamentals.pdf
for some discussion on assumptions on the effect of AC magnetic fields on humans. The calculations are based on the assumed characteristics of a human in a varying magnetic field. See page 5 and the table on magnetic flux density and assumed induced voltage. Note these are the induced voltages around a waist of 1 meter and are in the millivolt range. Also note the current desnities per sq-meter, rather low current per sq-cm. At 5000 mG their density is about 0.14 microA/sq-cm.
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