PIEZO SENSOR DRIVERS
They focused on monitoring the heart rate of drivers to determine the drowsiness level for safe driving. developed a signal-processing algorithm to extract the essential vital signs from a noisy signal. The method was not sufficiently robust in extracting the respiration rate because of the difficulty of finding the RR reference value due to environmental noise 26. used a piezoelectric sensor to measure respiration and extract ballisto-cardiogram (BCG) waveforms using a proprietary algorithm.
These signals can be obtained from the recorded signal by applying simple filters 25. The piezoelectric sensor was able to record respiratory movements, seism-cardiogram and heart sounds. The patient’s ECG signal was simultaneously recorded to provide a time reference of the cardiac activity. extracted vital signs by simply filtering the piezoelectric signal. Piezoelectric transducers incorporating single or multiple arrays have been utilized for the noninvasive monitoring of vital signs 24. Furthermore ECG device that has a capacitive electrode with a shield over conductive foam, and household monitors for heart rate based on ECG techniques using a chest strap 23. For example, Photo-plethysmography (PPG) sensors, which operate by observing the effect of blood engorgement and composition on light absorption during the systole phase 22. Other noninvasive sensors have been implemented in the field. A stepped frequency continuous wave (SFCW) radar is also used to measure the heart rate and respiration by transmitting high average power pulses with long duration and narrow bandwidth, then a signal-processing algorithm based on the state space method is applied to extract cardiac and respiration rates from the data measured on a human subject using SFCW radar 21. Noninvasive vital sign monitoring, which includes measurement of pulse oximetry 18, capnography, blood pressure (BP) measurement, and the standard five-lead electrocardiogram 19, has been used for patients who are in the intensive care unit 20 and in the operating room. The systems used to monitor vital signs may prevent diseases and enhance quality of life, thus reducing the costs of health care 17. Measuring vital signs (such as respiration rates, blood pressure, and heart rates) continuously and remotely without touching the patients can be an invaluable tool for physicians, as it can be used to make life-and-death decisions rapidly and make better decisions when long-term patient data are available 16. Researchers have recently focused on developing a remote non-contact sensing system having the ability to perform accurate long-term continuous monitoring of human vital signs. These vital signs are extracted from the acquired signals that enable more effective safeguarding of health by allowing for the early detection of any disease or abnormality 13– 15. Various methods and systems have recently been developed to monitor such vital signs 6– 12.
Vital signs, such as electrocardiogram (ECG) measurements, heart rate 2, respiration rate 3, systolic pressure (SP), and diastolic pressure (DP) 4, along with pressure pulse play an important role in determining the state of health of a subject 5. Monitoring vital signs is essential for daily health and medical diagnosis 1. All the results were validated step by step by a conventional apparatus, with good agreement observed. The piezoelectric and the convolution theories along with Fourier transformation are applied to extract the corresponding cardiac activity signal from the respiration signal. A representative model that incorporates the cardiac and respiratory activities is developed and adopted. During breathing, the measured voltage signal is composed of the cardiac cycle activities modulated along with the respiratory cycle activity. The induced vibration is then captured by the piezoelectric sensor placed at the chest surface, which produces an electrical output voltage signal conformally mapped with the respiration-cardiac activities. The contraction and expansion of the heart muscles, as well as the respiration activities, will induce a mechanical vibration across the chest wall. This work further contributes to the extraction of the corresponding representative vital signs directly from the measured respiration signal. The subject typically needs to hold his or her breath to eliminate the respiration effect. Piezoelectric sensors have been utilized to collect a corresponding representative signal from the chest surface. The monitoring of vital signs plays a key role in the diagnosis of several diseases.