i am working on a project, and i need some method by using that my system can make difference in the weight placed on the given board. i want to make my board so sensitive that it can generate two different signals for two different weights, weight may be of 1 gm and 2 grms.

 

If it's just an "A or B or none" weight detection, you just need a spring loaded platform. place a switch on top that is activated only when the platform is in the full
up position, and a switch below that is activated only when the heavy weight is placed on it. When neither switch is activated, the platform is in the middle position,
indicating the lighter weight. Is this what you're looking for?

If this is a homework project, ignore this message.

Rufus

 

Resolving a 100% difference shouldn't be too taxing. Look up load cells and strain guages. These are quite expensive. To take advantage of cheap but impressive technology consider a bladder with a solid state pressure
transducer under your board. These are available for very low pressures and less than $10 at DigiKey and Jameco.

Regards

cww