El Campo Magnético Generado por las Bobinas de Helmholtz y sus Aplicaciones a Calibración de Sondas

Abstract

Las bobinas de Helmholtz habitualmente se usan para establecer una zona de campo magnético conocido y uniforme para diversas aplicaciones. Es importante conocer la zona donde dicho campo magnético es uniforme con las distintas variables espaciales x, y, z. En la zona donde se genera un campo magnético uniforme, se pueden hacer las calibraciones de sensores magnéticos y sondas de campo magnético, en un rango de bajas frecuencias. Este trabajo se dedica a calcular y medir el campo magnético generado por las bobinas de Helmholtz y determinar la uniformidad y la exactitud del campo magnético respecto al centro de simetrı́a del sistema estudiado.

Loop Antenna Characterization for ELF and SLF Measurements

“…As the only difference between them is the number of turns, the one with more turns has a bigger inductance (providing though a higher amplification of the signal under test) but has a larger series-resistance in return. In order to make precise measurements, the loops have been calibrated using a pair of Helmholtz coils [15] and their antenna factor have been measured for frequencies up to 10 kHz. These measurements are in agreement with the theoretical Antenna Factor curves.…”

“…Using the Helmholtz coils [15] and the measurement scheme in Figure 5, a uniform Magnetic Field is generated in the space between the coils, in which the loop antenna is placed.…”

“…The magnitude of this Field depends on the geometrical characteristics of the Helmholtz coils and the current flowing trough them. This Magnetic Field can be computed with equation [15]:…”

“…The antennas under test were constructed with a copper cable of diameter 0.7 mm. Considering µ = µ 0 and σ Cu = 5.96 10 7 S/m, the impedance of two long wires (of the same length that the loops) at low frequencies are then Z N =180 ≈ 13.8 Ω + j ω 15.84 µH (15) Z N =300 ≈ 23 Ω + j ω 26.4 µH…”

Magnetic variation in construction steels under tensile stress. Empirical research with Helmholtz coils

“…When using this type of coils in industry, it is essential to know its intensity and uniformity and to delimit the region where the generated magnetic field is uniform. One of the most important applications of these coils is the possibility of measuring the magnetic field generated by electronic devices, with the aim of studying its behaviour in wider systems (9). The magnetic field to be determined can be situated in the far or the near field region (10,11).…”