Medical Applications User Guide (pdf) - Freescale Semiconductor
Medical Applications User Guide (pdf) - Freescale Semiconductor
Medical Applications User Guide (pdf) - Freescale Semiconductor
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Heart Rate Monitor<br />
5.1<br />
Introduction<br />
Heart rate monitors measure the heart rate during exercise or vigorous activity<br />
and gauge how hard the patient is working. Newer heart rate monitors consist<br />
of two main components: a signal acquisition sensor/transmitter and a receiver<br />
(wrist watch or smartphone). In some cases, the signal acquisition is integrated<br />
into fabric worn by the user or patient. MCUs analyze the ECG signal and<br />
determine the heart rate, making possible to implement a simple heart rate<br />
monitor with an 8-bit MCU.<br />
5.2<br />
Heart Signals Overview<br />
Figure 5-1 shows a typical heart signal. In this<br />
signal, the heart muscles generate different<br />
voltages. P represents an atrial depolarization.<br />
Q, R, S and T represent the depolarization and<br />
repolarization of the ventricles. Each time this<br />
signal is present, a heartbeat is generated.<br />
The principal purpose of this application is<br />
to provide a heartbeat average, so it is only<br />
necessary to work with the QRS complex (see<br />
section 5-4, Obtaining QRS Complexes). For<br />
this reason it is important to develop analog<br />
and digital signal conditioning. First, the signal<br />
is amplified and the noise is filtered, and then<br />
the QRS complex can be detected.<br />
freescale .com/medical 31
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