Week 6

After a few weeks searching for the best electrodes, Alhamdulillah, finally I have found the best electrodes or EMG sensors. Surface EMG Sensor from Delsys are fulfill the criteria that we want to this project.

Through my reading, I understanding of the design of the Delsys Surface EMG Sensors is crucial for the proper use. The first concept to consider is that the sensors rely on differential amplification. This means that the signal is detected at two sites, the signals are subtracted, and the difference is amplified. As a result, any signal that is “common” to both detection sites will be removed, and signals that are different at the two sites will be amplified. Most noise is “common” to both detection sites and is removed. The desired surface EMG signal is different at the two sites and is amplified. In the double differential model, the signal is detected at three sites and the subtraction procedure is performed twice to allow even greater focus on

the desired muscle and to eliminate crosstalk.

The second concept to consider is the fixed parallel bar arrangement of the skin contacts. Muscle fibers run longitudinally in a muscle. As a result, the electrical activity of the muscle also propagates predominantly along the length of the muscle. Each Delsys EMG Sensor has an arrow on top that should be aligned along the length of the muscle so that the parallel bar detection sites transect the muscle fibers. The parallel bar arrangement, in contrast to circular contacts, ensures that a maximum number of muscle fibers are monitored in a given location. The fixed distance between the contacts ensures that measurements are reproducible since changes in the distance between detection surfaces would affect the detected signal.

Figure 1 : Electrode