rotary measures?

Question

i have to measure lengths of paper when transferring from a 4 inch diameter roll to a 2 inch, typically in 4,5,8.and 10meter lengths.i use an approximate method based on the number of turns it takes to roll off 1 metre. and multiplying it by the number of metres i need. obviously,however,the diameter of the smaller roll increases the more paper is rolled on.making this method increasingly more inaccurate the more paper required.does anyone know of a wheel measuring device that would be in contact with the paper on the larger roll,giving a more accurate read out?

Answer 1

the simplest form would be a rubber wheel of known length and a counter to keep track of revolutions. below is a link to a mechanical system. I have not performed and extensive web search for an automated plc type but I'm sure they're out there