ETS-Lindgren 6404 Helmholtz Coil - Manual (Page 13)

Theory of Operation | 13
4.0 Theory of Operation
Before operating any components, follow the
safety information in the ETS-Lindgren
Product Information Bulletin included with your
shipment.
The basic premise of a Helmholtz coil is that it produces a homogeneous
magnetic field in its center which is directly proportional to the number of turns in
the coils and the current applied to them. A Helmholtz coil is a parallel pair of
identical circular coils spaced one radius apart and wound so that the current
flows through both coils in the same direction. The winding results in a very
uniform magnetic field between the coils with the primary component parallel to
the axes of the two coils. The uniform field is the result of the addition of the two
field components parallel to the axes of the two coils and the difference between
the components perpendicular to the axes. The primary purpose of this device is
to provide a uniform, low frequency magnetic field for susceptibility testing of
electronic equipment.
The magnetic field strength (H) produced by a given AC or DC current
through the coil pair is given approximately by the formula
R
NI
H 899 . 0 ≈
• H is the magnetic field in oersteds
• N is the number of turns per coil
• I is the coil current in amperes
• R is the coil radius in centimeters