Magnetomodulation sensor of a weak magnetic field based on HTS (Bi, Pb)2Sr2Ca2Cu3Ox ceramics

We studied the possibility to develop the magnetomodulation sensor of weak magnetic field based on the HTS (Bi, Pb)(2)Sr2Ca2Cu3Ox ceramics with the operational temperature similar to 77 K and critical temperature similar to 105 K. The sensors involved two coils (excitation and signal ones), which were closely wound on a cylindrical HTS ceramic core. The core length was 10 mm, and the core diameter was similar to 2.5 mm. It was found that the magnetic sensitivity S-U (S-U = d U-2/dH(0), where U-2 is the second-harmonic signal) for such sensors depends on the. excitation frequency in the range similar to 1-50 kHz, and on the excitation current, For the excitation current similar to 25 mA and excitation frequency similar to 50 kHz, the highest value of sensitivity S-U similar to 390 V/T was attained. When estimating the weakest magnetic field, which was detected by the sensor fabricated, we made allowance for the noise characteristics and errors of measurement devices used. The weakest detected field was similar to 0.5 nT in the absence of shielding from the terrestrial magnetic field and from the magnetic fields, which corresponded to industrial noise. (c) 2006 Elsevier B.V. All rights reserved.