Pd. Dimitropoulos et Jn. Avaritsiotis, A micro-fluxgate sensor based on the Matteucci effect of amorphous magnetic fibers, SENS ACTU-A, 94(3), 2001, pp. 165-176
The design, construction and performance of a novel micro-fluxgate sensor i
s presented in this work. The sensor is based on the large Matteucci effect
that is observed in amorphous fibers of typical stoicheiometry Fe77.5Si7.5
B15 after proper annealing. The sensor requires a single planar coil to fun
ction, which was constructed with conventional printed-circuit techniques a
long with the sensor signal conditioning circuitry. A new signal extraction
technique was applied that is superior to the conventional second-order-ha
rmonic concept, as far as sensitivity and signal-to-noise ratio are concern
ed. A conventional fiber, with diameter 125 mum, and a glass-covered fiber,
with core diameter 20 mum and glass-cover thickness 20 mum, were used as m
agnetic cores in the fluxgate sensor. The amorphous fibers were mounted, su
bsequently, above a planar coil by soldering each two ends without any furt
her mechanical treatment, like bending or twisting. Current annealing was p
erformed before mounting, for both magnetic core types in order to optimize
the inductive response of the fibers. The sensor sensitivity, before ampli
fication, was measured to be 74000 V/T. The low magnetic noise observed all
ows for a relatively high overall precision, which in the case of glass-cov
ered fiber has been verified to be 60 nT; this figure may easily improve by
known signal conditioning techniques. The overall sensor head dimensions a
re 60 mm x 30 mm. Further scaling down may be achieved by means of advanced
lithographic techniques in the case of glass-covered amorphous fibers only
, which exhibit significant Matteucci effect in lengths down to 5 nim. (C)
2001 Elsevier Science B.V. All rights reserved.