New to Arduino-Pulse Sensor- Pulse data is not stable shows 200

Hello,

I have purchase arduino uno board and pulse sensor. i followed the procedure for downloading on board as given in manual.
after long struggle i am able to see the pulse rate on screen, but the pulse rate is not stable.
it starts and going to 200 and remain there some time come to lower but suddenly shoot and goto 200.

please help me why the data is not stable. thanks in advance

please post your code
please post link to datasheet of pulse sensor
please post schematic