Toward Sensor to Reproduce Human Sense - The Electronic Nose Artificial Olfaction Technology - page 131

Fig. 5.7 Bio-signal processing

Analog
processor

Measurand Sensor Conditioner

Analog
Processor

DAC DSP ADC

Fig. 5.8 The basic signal processing

• Biomedical application: The biomedical signal is acquired and processed with
some diagnostic, monitoring or other goal in mind. Classification may be con-
structed according to the field of application e.g., cardiology or neurology. Such
classification may be of interest when the goal is, i.e., the study of physiologic
systems.
• Signal characteristic: From point of view of signal analysis, this is the most
relevant classification method. When the main goal is processing, it is not
relevant to the source of the signal of to which biomedical system it belongs;
what matters are the signal characteristics.

In another way, biological signals can be classified into two main groups: the
deterministic and the stochastic (or statistical) signals, as shown in Fig. 5.9 . Such
as a beating heart or respiration generates signals that are also repetitive. The
deterministic group is subdivided into periodic, quasi-periodic, and transient sig-
nals. The stochastic signals are subdivided into stationary and non-stationary
signals [ 18 ]. Groups of cells depolarize in a more or less random fashion such as
muscle cells generating electromyography or nerve cells in cortex. Deterministic
signals are signals that can be exactly described mathematically or graphically.
Real-world signals are never deterministic. There is always some unknown and