Why not looking at the micro Speed Elovis sensor (non-contact speed and length measurement)

A new contactless technology is available to replace the technology with encoder and wheel in contact with the material. Laser-based technology is capable of measuring speed and displacement, thereby eliminating the slippage and maintenance problems associated with wheel systems. In addition to the much greater accuracy of this technology allows to self-finance its investment. The system with an error of only. 05% VS 2% for coded wheel systems allows you to save thousands of dollars annually in material and customer complaint.