Equipment for SEMG Signals Acquisition and Processing

Abstract

Electromyography is a technique for evaluating the electrical activity of muscles. The EMG signal measurement is useful for the detection and analysis of muscle tissue activity. If the EMG signal is acquired from the surface of the skin, the signal is called Surface EMG or SEMG. The SEMG signal is a small amplitude signal which is strongly affected by noise. SEMG signal processing increases the signal-to-noise ratio (SNR), optimizes the electrode-skin impedance, and cancels the crosstalk of adjacent units. The SNR depends on external electromagnetic disturbances, and also on the quality of the equipment involved in the acquisition of EMG signal, like electrodes, preamplifiers, analogue-to-digital convertors (ADC) and digital processing blocks. This paper presents the development and implementation of a SEMG signal acquisition block. This block amplifies, filtrates, converts and memorizes in digital format for further processing the SEMG signal. The main IC is TI’s ADS1298 Low-Power, 8-Channel, 24-Bit analogue front-end for biopotential measurements. Our implementation uses in front of the ADS1298 a set of instrumentation amplifiers, AD620, in order to increase the SNR. The ADS1298 transfers the digital data to a microcontroller via a SPI interface. We intend to use the Xilinx XUPV5 platform to digitally process the signal, so this board is interfaced with the microcontroller via a parallel interface.