# What happens if the web jumps suddenly during chasing—won't the sensor lose track?

> In chasing applications, process upsets can cause the web to wander significantly—due to splice passage, tension changes, or roll eccentricity. This exposes a critical weakness in narrow-range sensors: Narrow sensor problem: If the target (line, edge, or pattern) moves outside the sensor's field ...

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

**Source:** https://live-roll2roll.pantheonsite.io/resources/faq/what-happens-if-web-jumps-suddenly-during-chasing-wont-sensor-lose-track

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## Question

What happens if the web jumps suddenly during chasing—won't the sensor lose track?

## Short Answer

Narrow-range sensors lose tracking during sudden web wander. Roll-2-Roll's wide-range sensors (up to 960mm) maintain lock on the target, and the SCU5/SCU6x controllers include "Lock on Lost Edge" protection that inhibits the actuator if tracking is lost.

## Detailed Answer

In chasing applications, process upsets can cause the web to wander significantly—due to splice passage, tension changes, or roll eccentricity. This exposes a critical weakness in narrow-range sensors:

- Narrow sensor problem: If the target (line, edge, or pattern) moves outside the sensor's field of view, the system loses tracking. With older controllers lacking edge-loss protection, the actuator continues driving in one direction until it reaches its limit—potentially damaging equipment or producing scrap.
- [Roll-2-Roll® Sensors](https://r2r.tech/products/sensors) + [SCU5](https://r2r.tech/products/sensor-controller/scu5)/[SCU6x](https://r2r.tech/products/sensor-controller/scu6x) advantage: Wide-range sensors (up to 960mm) provide a large capture window that maintains lock on the target during extreme wander events. Additionally, the [SCU5](https://r2r.tech/products/sensor-controller/scu5) and [SCU6x](https://r2r.tech/products/sensor-controller/scu6x) controllers include a "Lock on Lost Edge" feature that inhibits actuator movement if the edge is lost—preventing runaway conditions. For line/contrast guiding, loss of contrast also inhibits the actuator.

**Example:** An [ODC 288](https://r2r.tech/products/odc-288) sensor provides 288mm of sensing range. If the web edge wanders ±100mm during a splice, the sensor never loses sight of it—and the controller keeps tracking smoothly.

**Category:** Technical

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## About Roll-2-Roll Technologies

Roll-2-Roll Technologies designs and manufactures patented fiber-optic web position sensors and advanced web guiding controllers — the precision measurement and control core of modern roll-to-roll manufacturing. Spun out of Oklahoma State University's Web Handling Research Center and trusted by Fortune 500 medical, battery, and nonwovens manufacturers, our patented sensors work without recalibration at ±0.1mm accuracy up to 760 mpm — typical customer outcomes are 50%+ less downtime and payback under six months. Headquartered in Stillwater, Oklahoma, our team of PhDs, controls engineers, and industry veterans extends the sensor + controller core into complete web guide systems including stepper-motor-based linear actuators (RLA, BLA, LHS).

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