An impact sensor is an accelerometer-based device on a forklift that detects a shock above a set threshold, records when and where it happened and which operator was logged in, and can trigger an alert or lockout.
Impact sensors answer a question that unreported damage leaves open: when did this rack, door or truck get hit, and by whom. Thresholds are typically set in levels, so a light bump is logged and a heavy impact alerts a supervisor or, on some systems, puts the truck into slow mode or locks it until it has been checked. Paired with operator access control and a camera, the event comes with a name and a clip, which supports coaching and accident investigation.
Thresholds need tuning: too sensitive and potholes, dock plates and normal pallet handling fill the log; too coarse and real collisions go unrecorded. An impact sensor reports after the event, so it is a lagging and accountability tool, not a way to prevent the first collision. Logs of minor impacts can still act as an early signal of risky driving or poor layout. Racking struck by a truck should be inspected regardless of what the sensor recorded. The impact cameras post explains how sensors and cameras combine.