Electret condenser microphone as sensor in arterial pulse recording device

One of the human pulses could be detected on an arterial radial that represents the human health condition. Several sensors could capture the pulse signal. However, it still needed a sensor with a small dimension and lightweight. One of the sensors that comply with those specifications is an electret condenser microphone (ECM). The ECM was designed to pick up the signal from the human radial arterial pulse. The ECM pick up system was equipped with an instrumentation amplifier and a signal processing system. The characteristic of the ECM was analyzed using a sixth-order polynomial equation. The equation was used to reconstruct the signal, which flattened the frequency response at the range of 0.5-4.5 Hz. The signal processing consists of an FFT, peak detection and a sixth-order anti-polynomial computational unit which is implemented in a computer. The minimum error was found at 1.5 Hz, which is closed to the designated frequency of the arterial pulse normal frequency.