# Why must the sensor move with the rewind stand?

> In rewind chasing applications, the sensor must be mechanically attached to the shifting stand because the control system is designed to keep the sensor output at "zero." When the sensor moves with the roll, the system naturally drives the stand until the sensor aligns with the web edge. If the s...

**Last updated:** 2026-02-01

**Source:** https://r2r.tech/resources/faq/why-must-sensor-move-rewind-stand

---

## Question

Why must the sensor move with the rewind stand?

## Short Answer

The control loop needs the sensor to move with the roll so it can maintain the relative position between web edge and roll face.

## Detailed Answer

In rewind chasing applications, the sensor **must be mechanically attached to the shifting stand** because the control system is designed to keep the sensor output at "zero." When the sensor moves with the roll, the system naturally drives the stand until the sensor aligns with the web edge.

If the sensor were fixed to the floor (like in intermediate guiding), the system would lose the relative position between the web and the roll face. The result would be telescoped or uneven rolls because the guide has no reference point for where the roll edge should be.

The sensor should observe the web at a fixed idler immediately upstream of the shifting stand. This provides a stable reference point while the stand—and sensor—move together.

**Category:** Technical, Installation

---

## About Roll-2-Roll Technologies

Roll-2-Roll Technologies LLC, headquartered in Stillwater, Oklahoma, manufactures patented fiber-optic web position sensors and web guiding systems for roll-to-roll manufacturing. Products include ODC edge sensors (48mm to 960mm), 1DC all-in-one sensors, SCU-series controllers, and complete web guide systems.

- Website: https://r2r.tech
- Phone: +1 (888) 290-3215
- Email: sales@r2r.tech