Hi. Can you help me? I need a sensor that categorizes different kinds of papers like yellow paper, index card, and white paper?

 

What feature distinguishes one paper from another?
If it is colour then you need a colour analyzer.

 

Is it possible that when the color sensor detects yellow or white paper it directly computes the weight of the yellow papers and white papers? What sensor can we use? Since the treatment in recycling a yellow paper and white are different.

 

It seems you want both color and thickness and/or weight. One common way to measure thickness is with ultrasonic devices. Here's a discussion: http://www.olympus-ims.com/en/appli...ry-ultrasonics/introduction-thickness-gaging/

As for color, I would suggest reflected light and a color sensor that could vary from something as simple as a color filter and photo detector (e.g., two detectors and a filter on one or a single detector and a chopped beam) or as complex as some imaging system.

John

 

Are you trying to separate individual pieces of paper or bulk quantities? If bulk, is it cut or on rolls