RESUMEN
The aim was to analyze the inteiference in a signal acquisition module (SAM) EMG1000 (Lynx--10(9) Ohms, 16 bits and range of +/-1 V), with active surface electrode (Lynx--gain 20, IRMC > 100 dB) placed over the belly of the brachial biceps of 18 healthy, sedentary volunteers, without osteomyoarticular pathologies in the upper members. Initially, the intrinsic noise of the SAM was assessed by means of a short-circuit between the simple differential and the reference electrodes, and a second stage consisted of collecting the electromyographic signal at rest of the brachial biceps muscle in 4 different procedures. (1) SAM and desktop in the electrical network (EN); (2) SAM in the battery and desktop in the EN; (3) SAM in the EN and desktop connected to the fibre optic (FO) and (4) SAM in the battery and desktop in the FO. The rest signal was collected for 10 seconds and repeated 3 times. RMS and median frequency were assessed with the software Matlab. Under conditions 1, 2 and 3 there was great interference in the signal by EN. Whereas under condition 4, the interference was eliminated. According to the results, the electrical insulation proposed was efficient in eliminating the noise, guaranteeing the quality of the acquired signal.