Wiktionary
check weigher
n. A form of dynamic scale that weighs products as they come off a production line
Wikipedia
Check weigher
A checkweigher is an automatic or manual machine for checking the weight of packaged commodities. It is normally found at the offgoing end of a production process and is used to ensure that the weight of a pack of the commodity is within specified limits. Any packs that are outside the tolerance are taken out of line automatically.
A checkweigher can weigh in excess of 500 items per minute (depending on carton size and accuracy requirements). Checkweighers can be used with metal detectors and X-ray machines to enable other attributes of the pack to be checked and acted upon accordingly.