H-field sensor measurement errors in the near-field of a magnetic dipole source

A pair of error relationships is derived to describe the sign and magnitude of the error incurred in the measurement of the near magnetic field strengths of an elementary magnetic source. Analyses are performed for two different relative orientations of the source and small-loop sensor, the source being an elementary magnetic loop. First, an error analysis is performed for the situation in which the sensor is aligned coaxially with respect to the source. The second analysis investigates the near-field error associated with a coplanar source and sensor relative orientation. Results of the analyses indicate that in the case of a coaxial arrangement of small-loop source and small-loop sensor, the incurred error is negative (i.e. measured magnetic field strength is lower than the actual value at the loop sensor´s center). For a coplanar arrangement of the magnetic source and small-loop sensor, a positive measurement error is incurred. It is also shown that effects due to mutual coupling between the source and small-loop sensor are minimal