The electromyograph, also known as an EMG, is widely used in medical applications. It is an instrument that measures the degree of bioelectrical activity occurring within a muscle to determine whether a muscle is in a state of spasm. As muscles are activated, they generate action potentials that flow through the resistive medium of the tissues. The voltage gradients produced may be recorded as the myoelectrical signal. An EMG can therefore be used to investigate when and how strongly a particular muscle is contracted.
The EMG signal spectrum exists largely in the low frequency range of 50 to 300 Hz. The voltage produced during normal muscle contraction is generally in the millivolt range. Since the voltage from the muscles is normally a small signal, commercial EMGs have high common mode rejection-ratio and low-noise amplification.
The project that we undertook was to construct a simple functional electromyograph which could be used on a variety of anatomic locations. The proposed EMG would also present the EMG signal in three ways: filtered, filtered and rectified, and filtered rectified and integrated.