Why Sensitivity Drops After Line Speed-Up: Matching Conveyor Speed to Detection Capability

Many plants find that after a line upgrade, the same metal detector begins missing fine metallic fragments. This relates to the detection principle: the signal generated when metal passes through the coil is proportional in duration to the inverse of speed. The faster the product moves, the shorter the signal, and the less time the circuit has to evaluate it. At high speed, the ability to respond to small contaminants therefore decreases. This is physics, not a fault in the equipment.

When selecting equipment, line speed should be provided to the supplier alongside detection accuracy. A quoted sensitivity figure is usually measured under specific speed conditions. If actual running speed is clearly higher than the reference value, the achievable detection level must be reassessed. Some models offer speed adaptation or multi-frequency operation to balance throughput and sensitivity within a range, but a reasonable match between speed and accuracy is still required.

For lines that have already been sped up, run a practical verification first: pass Fe and SUS test pieces of different sizes repeatedly at actual running speed, record the detection results, and then adjust parameters or moderately reduce throughput. If the cycle time genuinely cannot be lowered, consider a model with a detection aperture closer to product size, or evaluate X-ray inspection as a supplement. Logging speed in routine verification records is also an effective way to keep detection stable.