Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (bkci)

5.3. Bioinformation acquisition
Biological signals are often very small and typically contain some unwanted noise or interfer‐
ence. Such interference could determine the effect of obscuring relevant information that may
Advances in Bioengineering
218

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be available in the measured signal. Noise can be extraneous in nature, arising from sources
outside the body, such as thermal noise in sensors or noise in the electronic components of the
acquisition system. Noise can be intrinsic to the biological media, meaning that it can arise
from adjacent tissues or organs. ECG measurement from the heart can be affected by bioelectric
activity from the adjacent muscles.
In order to extract the meaningful information from biological signals, sophisticated bioinfor‐
mation acquisition techniques and equipment are commonly utilized and explored. Equip‐
ments with high-precision low-noise are very necessary to minimize the effect of unwanted
noise. Basic components include sensors, amplifiers, analog signal conditioner, data acquisi‐
tion, data storage and display, digital signal processing circuit. The bioinformation acquisition
procedure is shown in figure 35.
Figure 35. Procedure of obtaining biological information
In figure 35, sensors feel the biological signal that is being observed into an analog signal
conditioner to adapt the requirement of data acquisition system. Here data acquisition system
converts the analog signals into a calibrated digital signal that can be stored. Digital signal
processing techniques are employed here to reduce the noise and extract additional informa‐
tion that can improve understanding of physiological meaning of original parameter.
Throughout the data acquisition shown in figure 35, it’s very critical that the information and
structure of original biological signal of interests be faithfully preserved. Because these signals
are often used to help people diagnose the pathological disorder. The procedure of analog
signal conditioner, data acquisition system, analog amplifying and signal filtering, and A/D
conversion should not generate misleading or untraceable distortion. Signal distortion would
lead to an improper diagnosis on biological body.
In bioinstrumentation, after biological signal has been detected with an appropriate sensor, it
is amplified and filtered. Operational amplifiers are electronic circuits that are used to adjust
the amplitude or size of biological signal. Analog filter may be used to remove the noise hiding
in biological signal or compensate for distortions caused by sensors. Amplification and
Biomedical Sensor, Device and Measurement Systems
http://dx.doi.org/10.5772/59941
219

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filtering of biological signal may be necessary to meet the requirement of hardware specifica‐
tions of signal conversion procedure. Continuous signal needs to be limited to a certain band
of frequencies before signal can be digitized with an analog-to-digital converter, prior to
storing in a digital computer.