| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 106 === To solve one of the major problems in recording biopotentials, which is the unwanted 60Hz interference produced by power line, an automatically adjusting resistors design is proposed. Three custom made electrodes composed of three copper coins covered by copper sheet, and a custom-design amplifier (ASIC) are used as a part of the recording setup. Goertzel algorithm and undersampling are implemented to detect interference. They save power compared to Fast Fourier Transform (FFT) for interference detection and a reduced sample rate from 121Hz to 80Hz. Off-the-shelf dual SPI digital potentiometers with 0 to 10kΩ tuning range are used to offset the imbalance of impedance from electrodes. A microcontroller operates the Goertzel algorithm and the dual potentiometers. Continuously detecting the interference level by Goertzel algorithm, the dual potentiometers keep adjusting the value until the impedance balance is achieved. A demonstrator setup is produced and tested on the bench. The testing waveform is recorded by Labview and evaluated by Matlab. The prototype consumes 18.36mW, including amplifiers, two microcontrollers, and dual digital dual potentiometers.
|
|---|
