Image Processing Reference
In-Depth Information
(Cuesta, 2001; Vidal et al., 2008; Vidal & Gatica, 2010) where the most important part
corresponds to the amplifying module because of a bioelectrical signal that represents a low
potential, and sophisticated amplifiers are required for obtaining and recording it (Vidal &
Pavesi, 2004; Vidal et al., 2008; Vidal & Gatica, 2010).
The following sections present experiences building a device for getting the ECG signal, and
works related to processing ECG signal.
3.1 Digital ECG design
Signals produced by bioelectric phenomenon are small potential values and due to this,
sophisticated amplifiers are required so as to easily obtain signal values (Vidal & Pavesi,
2004).
Against a physiologic backdrop, these ionic signals are transmitted at a fast-rate without
synaptic delay in both direction directed by the electric synapse transmission model. This
electric potential is later transformed in a mechanical signal as of using calcium ion that
comes from extracellular condition which is also useful for cooking calcium that is released
from the internal section of cardiac cells provoking a massive cardiac muscle like a sincitio
or functional unit (Clusin, 2008). In this sense, the main finality of an amplifier is to
increment the measurable level of the gotten signal by electrodes, avoiding any kind of
interference. The capacitive interference of the patient body, electrical fields of electric
installations, and other environment electronic devices are examples of interference or noise.
(Proakis & Manolakis, 2007) indicate that the quantification can be done using single pole
configurations or bipolar. In the single pole quantification, difference between a signal and a
common base is measured whereas the bipolar mode measures the difference of two voltage
sources (two electrodes) with respect to a common base where any interference voltage
generated at the quantification point appears at the amplifier input as common-mode
interference signals. Figure 5 illustrates this phenomenon in a bipolar quantification.
Fig. 5. Common-Mode Interferences in a bipolar quantification
A strong source noise which interferes on the ECG signal is the capacitive interference of the
patient body. This interference voltage is coupled to the ECG signal reaching values of 2.4 V
approximately. A value which is very higher than the ECG signals value range (0.02 mV to 5
mV). In addition to this interference, the capacitive interference due to the equipment or
device used to measure the ECG signal which is produced by the equipment power supply.
Another noise source is the denominated inductive interference that is caused by the electric
net which produces variable in time magnetic fields inducing extra voltages on the next of
patient electrodes (Townsend, 2001).
Search WWH ::




Custom Search