An EMG signal that has not been amplified has typical charges between a few microvolt and 2-3 millivolt
when reading on the skin. The signal is generally amplified by a factor of at least 500 (e.g. when using preamplifiers)
to 1000 (passive cable units). The Input impedance of the amplifier should have a value of at
least 10x the given impedance of the electrode. Winter (11) suggests an input impedance of 1-10 MegaOhm.
The frequency range of an EMG amplifier (bandpass settings) should start from 10 Hz highpass and go up
to 500 Hz lowpass. Any Notch filtering (to cancel e.g. power hum) needs to be avoided because it destroys
too much signal information (SENIAM, ISEK). Both cable and telemetry systems are available and applied
concepts range from handheld 1or 2 channel - Biofeedback units up to 32 channel systems for complex
and multi-parametric setups (Fig. 17).