working with a piezo sensor

[qureishi]

hello everyone,
i m trying to use a piezo sensor ! when i put the sensor on my radial artery, a ditchy at peaks kinda wave is observed on oscilloscope, but when i put the tip of my index finger on the sensor, a pure sine is obtained !
i m unable to comprehend the info these observations are depicting and the reason of them being different !
kindly guide me ....
thanks

 

[chuckey]

You have not given us any relative information. At a guess the sinewave is "hum" picked up from the local mains wiring. The "ditchy" (what is that meant to mean?) waveform is the sensor picking up the pulses of blood flow.
Frank