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MGL SURFACE CURRENT ( j ) SENSORS

The MGL (Multi-Gap Loop) J-dot Sensors (Models S4, S5, S7, and S8) are half-cylinder loops mounted on conductive ground plates and positioned on conducting surfaces to measure the time rate-of-change of the surface current density (J_s) by means of the associated magnetic field.  They are identical to the basic MGL B-dot ground plane sensors except for (1) shorter baseplates, which simplify mounting on current carrying surfaces, and (2) connectors on the radial versions which are on the ground plate instead of protruding through it.  These sensors are passive devices requiring no power and have been used extensively in EMP test programs.

The half-cylinder sensors have two symmetrically located gaps which are combined by a series-parallel wiring arrangement to drive the coaxial output connector.  The output connector can exit either along the cylinder axis (axial version) or along a radius (radial version) as shown above.  In both cases the connector is at the edge of the ground plane, not below it as in the standard MGL-4(R), 5(R), 7(R), or 8(R) sensors.

PERTINENT EQUATION

	Vo = = sensor output (in volts)
where
	= permeability of free space (4π x 10 -7 H/m)
	= sensor equivalent area (in m2)
	= surface current density (in Amps/m)
	= angle between sensor axis and Js vector

Data Specification Sheet