Study On Magnetic Marker Monitoring Circuit And Signal Preprocessing

The principle of magnetic marker monitoring method is using the penetrability of magnetic field to non-magnetic shielding objects, such as human body, which can realize the three dimensional location in the in-visual condition, so it is widely used in medical fields. Compared with signal intensity location method, X-radiographic location method, ultrasonic location method and radioactive element labeled location method, it has the advantages of micro-invasion and simple operation.The paper mainly studies on the design of magnetic sensor array and signal preprocessing.Two kinds of magnetic location circuit are designed based on different theories. One is based on hall sensor array, and the other is based on magnetic sensor array. The former use hall sensors transform the changing of magnetic field to voltage signal, then the signal is filtered and amplified and transfer to the computer. The latter use magnetic flux transducer and its control chip measure the magnetic field. The aim is to search the better method for magnetic location through comparison experiment.The original signal sampled by the sensor array should be preprocessed to improve signal-to-noise ratio. Experiments proved that each of the two methods, the default threshold method of wavelet analysis and the smoothing average filter, has its strong point. The default threshold method of wavelet analysis can filter noise signal from the static magnetic field signal in most of the frequency range. While, the smoothing average filter can process the dynamistic signal better. In the paper, the two methods are integrated to process the magnetic signal, and it proved effective to improve signal-to-noise ratio.Experiment is the important part of the paper. The matching of hall sensors, sampling of magnetic signal, arrange of sensors, preprocessing and compensation of geomagnetism experiments are done respectively. With the comparison of two kinds of circuit, magnetic sensor array is more sensitive and stable than hall sensor array. In conclusion, magnetic sensor array combined with default threshold method of wavelet analysis has improved magnetic location precision.