May i know can i upgrade it to measure up to 100 meters?
If so which part have to change ? the circuit one or program?

Thanks.

 

6m Sensor

Beyond transducers, increasing range needs high sensitivity op amps and a good bit of noise rejection. The unit above has a good deal of it set up, but it is the cost of 4 basic ultrasonic rangefinders.

 

This thread was a hijack of - http://forum.allaboutcircuits.com/showthread.php?t=20990

 

For anything beyond 20 feet, you'll more than likely end up using a laser ranging solution.

Expense goes up by a factor of 10 or so.