A checkweigher is essentially a high-speed quality control scale incorporated into a production line.. As packaged items move along the conveyor, the checkweigher uses a highly accurate sensor (a load cell) to measure the weight of every single product in motion. It instantly compares this measurement against a set target weight and acceptable tolerance. If the product is found to be either underweight or overweight, the machine automatically uses a mechanism (like a pusher or air jet) to reject the faulty item from the line, ensuring that only products meeting strict quality and legal weight standards continue on to be shipped.