Circuits Signals

EKG amplituede

10 uV to 5mV

EKG Frequency

0.05Hz to 150Hz, generally 100Hz so sample at 200Hz

EEG Amplitude

10 to 200 uV (microvolts)

EEG frequency

0.5-30Hz, so sample at around 60

EMG amplitude

0 to 10mV

EMG frequency

0-500Hz for surface (sample at 1000Hz)

0-1000Hz for indwelling

Nerve potentials amplitude

50 to 100mV

Nerve potentials frequency

0.05-500Hz

Analog

A continuous electrical or physical signal that varies over time where its value can be any point within a range

Digital

A signal of discrete values taken at fixed timed points

Frequency content analog

Different frequencies and their corresponding amplitudes that make up the analog signal

Bandwidth

Analog signal’s total range of frequencies

Background electrical frequency

50Hz for Europe, 60Hz for US

Nyquist theorem

To reconstruct a continuous signal from its sampled digital form, sampling rate must be at least twice the highest frequency component of the original signal.

Aliasing

A distortion that occurs when an analog signal is sampled at too low of a rate

Inverting Amp

A = -Rf/Ri

Non-inverting amp

A = 1 + Rf/Ri

Differential Amplifier

Vout = (Rf/Ri) (Vin2 - Vin1)