ABSTRACT
A photoplethysmograph (PPG) is a method o f detecting human pulse w ith
principal of correlation anal ys is. A PPG is described that performs a frequency anal ys is
of the peripheral volume pulse wave. A Trans-impedance amp lifier is used to convert
current received from the photodiode to voltage for future processing. The pul se detecto r
receives information in terms of an analogue signal. Pulse carrier is low-frequency
signal with upper informative frequenc y. Therefore to ra ise the method perfo rm ance we
apply low-pass filte r, lOOHz. A low-pass filter passes relativel y low frequency
components in the signal but stops the high frequency components. The so-called cutoff
frequency divides the pass band and the stop band. In other words. the frequenc y
components highe r than the cutoff frequenc y will be stopped by a low-pass filter.
This project also develops a low noise Pul se Sensor through Corre lation Analysis
(Lock-In). The lock-In acts like an Amplitude Modulation used Multiplication of
reference signal and measured signal. Through corre lation anal ys is or lock-i n, noi ses
that exist in measured signal ca n be rejected. Lock-In is capable to improve the
Signal-to-Noise ratio significantly: The band-pass filter cuts simpl y out a more or less broad
part o f the no ise power spectrum in the vicinity o f the input signa l. he reby reducing the
average re lati ve no ise power at the output, or the relati ve rms noise vol tage.
respectivel y.
The purpose of thi s proj ect is to detect hum an pul se throug h their fin ger. It
prov ides vari ety of information such as the ir health y information.
