BLOOD pressure (BP) acts as one of the vital signs providing the useful information about cardiac output and elasticity of the blood vessel, and physiological variation. Therefore, the measurement of BP is helpful for a physician to understand and diagnose the integrity function of the cardiovascular system. The invasive method of measuring the blood pressure by inserting a catheter into the blood vessel to measure the arterial pressures accurately, still has the disadvantage of accompanying pain and contamination, and the side effects arising from inserting the catheter-tip into a patient's blood vessel. The various indirect methods of measuring BP such as Riva-Rocci and oscillometric and ultrasound, and tonometry method, etc. were developed to solve these problems [1]-[2].