Design of a data acquisition system on magnetic signal for magnetic localization and orientation system

The location and orientation of the wireless capsule endoscope inside the human body is very important for the gastrointestinal (GI) examination. To satisfy the requirement of the position and gesture information of endoscope, a magnetic localization and orientation system is built. The system uses a permanent magnet as excitation source to create the magnetic field, and consists of a magnetic sensor array, high performance analog multiplexers, precise and low noisy instrumentation amplifiers, a 16-bit analog-to-digital converter and an ARM controller. The magnetic field varies with the magnet's position and orientation and is detected by the magnetic sensor array which is around the human body. With the detected data, the position and orientation of the capsule endoscope can be computed by the efficient algorithm, so as to realize the real-time tracking. Obviously, the accuracy of detected data is critical to the tracking precision. However, the magnetic field signal is so weak and attenuates dramatically when the spatial distance between the magnet and the sensor increases. In this paper, we present an effective data acquisition system to accurately detect the weak magnetic signal. The experimental result shows that the average error is below 2.1mm when the distance between permanent magnet and magnetic sensor is up to 500mm, therefore, this data acquisition system can be used for the application of wireless capsule endoscope with the space of 1mx1mx1m