RESUMEN
Objective To design a system of conductivity tomography using focused magnetic fields for data acquisition. Method A frequency modulation detection circuit with array of sources was employed to implement multi-frequency measurement. In the circuit, a specially designed coil with good focusing property was used to improve spatial resolution of the image. Acquired data of frequency changes from the detector was stored in the memory operated by a ping-pang pattern, then the data was transmitted into computer by serial communication interface whose transmitting rate reached 115. 2 KHz. Result Frequency stability of the signal source in the system reached 0. 2%; the total harmonic distortion of the signal was less than -43 dB; the signal noise ratio of the source was from 58 dB to 62 dB. The storage capacity of memory was 131 072-word by 16- bit. The system has good frequency resolution, and is easy to be analyzed and processed by the software after data acquisition. The conductivity of the computed results agreed with that in the given model. Conclusion The system is effective to detect and reconstruct the conductivity of stratified biological tissue for its high sensitivity.