Use of Ultrasonic sensor for measuring distance........

What should be the duration of pulse according to you ?

akshaydusane

I assume you are now using a HC-SR04 not the original GH311

distance = (high level time×velocity of sound (340M/S) / 2,

By my calculations..
For an object 10cm away the pulse is 0.58 mS (580 uS).
For an object 4m away the pulse is 23.5 mS.
Over 4 metres (out of range),or no object present the pulse is over 23.5 mS.
With no object present the pulse is probably not more than 50mS.

According to you the delay of the pulse should be 23.5 ms....