Metal detector performance: how to test accurately?

Now this is a loaded question. Most industrial metal detection companies cringe when they are asked about performance. Why is this? Simply metal detector performance is based on many variables which change over time, some frequently others over long periods, and often can not accurately be duplicated in laboratory testing. 

So why do metal detector company’s rate performance in diameter size? The basic reason is that a sphere of metal is easy to produce, doesn’t change its profile shape as it enters the metal detector and is easily understood.  So is this a good way to measure the performance of my industrial metal detection system? Well for now it’s the best method for the vast majority of application. If you are producing cheese or bread products you need a simple repeatable method to test your equipment with. Same goes for companies manufacturing paper or carpet. 
Why is metal not being detected in my metal detector?
The testing method of all major metal detector companies is although repeatable it doesn’t reflect the real world. Rarely does a food manufacture have round sphere like metal contaminates in their product. Often they have wire or metal shavings from drillings in their products. This is a significant difference from the testing samples and often leads to confusion and misunderstanding with a metal detectors performance.  As a rule o thumb you should have your metal detector tested with the smallest piece of metal it can detect. This will help to catch and reject the normal contaminants found in today’s real world food production.