By the way, I want to design a digital balance with set option, on the other hand I don't have any idea about sensors for wieght.
can you achieve me to guide my goal?
No, we can not.
Are you going to measure feathers, or are you going to measure trucks?
You have not spent any time making a very concise description of exactly what kind of scale you want to build, so it is impossible to know if you should use load cells, force sensors, torque sensors, pressure sensors, optical strain gauges, mechanical springs with magnetic or optic measurement, ...
The best way to answer you: Switch from this site to Google. Think for a while. Then use your googling skillz and visit the huge number of sites specializing in measurements - espesially regarding weights/forces.