Here is how you can verify the accuracy and repeatability for any in-motion scale device. This procedure will outline the steps for an in-motion checkweigher, but it is identical for a conveyor scale.
Steps To Ensuring In-Motion Checkweigher Accuracy & Repeatability:
- Check the zero both statically and in-motion.
- Get a product that represents the product that you intend to weigh in-motion (dynamically). Then verify the exact weight of that product on a very accurate static scale. You now have what is known in the industry as a “test puck.”
- Turn the in-motion checkweigher ON (run the belt) at the speed that you intend to use the in-motion checkweigher in production.
- Apply your test puck to the infeed belt of the in-motion checkweigher to allow relative motion of the test puck-to-belt motion to stabilize before the test puck arrives on the in-motion checkweigher’s live section. Then collect the test puck after the in-motion checkweigher’s live section once weighing is complete.
- Record the checkweigher’s in-motion value.
- Repeat steps 4 and 5 at least 32 times. (No, we are not kidding!)
- Verify that zero did not change. If it did, you will need to start over.
- Verify that the test puck static weight is still the same value when you started. If it changed, you will need to start over.
Analyze the results by determining the highest and lowest values, the difference is the spread, then average all the in-motion values and compare against the actual static weight of the test puck. Don’t forget standard deviation calculations!
Make sure you store the values so you can compare them against future weighments.
Following the above steps, as tedious as they seem, will give you a clear picture of the true accuracy and repeatability of your in-motion checkweigher. Future testing with similar results will prove the performance is staying constant while variations with trends can indicate problems with the checkweigher.
If you have questions about the above procedure, contact us and we will be glad to help!