In the introduction of XR, the false rejection rate (FRR) and the detection rate (POD) are usually mentioned. The false rejection rate and the detection rate are the detection results of a product with a certain foreign object detection accuracy. The false rejection rate and the detection rate are usually mutually exclusive. The false rejection rate is high, and the detection rate should also be high. On the contrary, the false rejection rate is low, and the detection rate should also be low, Generally, if the accuracy detection standard is met, the detection rate should be guaranteed or the rejection rate should be reduced. For a certain product, the detection accuracy may be different in different areas, such as iron can milk powder, tank bottom, tank wall, and tank. On the premise of meeting the FRR, the POD of three parts is different, and the detection accuracy of the whole tank is usually guaranteed according to the worst accuracy.

The FRR and POD of XR are scientific and accurate, because each image is traceable whether it is a product that is mistakenly removed or has real foreign matter, which can truly reflect the practical significance of FRR and POD.

The principle of MD is different from that of XR. In addition to the elimination time, the real reason for the elimination cannot be restored. Generally, the reasons for the wrong elimination of MD are:

1. MD’s own reason (aging or individual damage of components, causing MD’s unstable operation, etc.)

2. Operating environmental factors (site vibration, high temperature, electromagnetic interference of other equipment, etc.)

3. Factors of the inspected product (product temperature change, product detection position change with product effect, etc.)

After the above factors cause the alarm, it is difficult to find out the real reason. This is why we usually only mention the improvement of the detection accuracy and the reduction of the error rejection in the introduction of MD products, rather than the reduction of the “error rejection rate”. Because there are many reasons that cause the error rejection, it is impossible to fully prove that MD is not a problem, and it is the error rejection caused by other reasons, which is difficult to prove. This is why MD usually does not mention FRR and POD.

FRR and POD are contradictory to each other, usually a result of compromise and balance. If both FRR and POD can meet the customer’s requirements, it is the best. If not, it depends on which FRR and POD is important. If the tested product is expensive and the subsequent processing cost of the rejected product is high, it may reduce the detection accuracy a little. If the inspected product is cheap and the processing cost is low, it is necessary to ensure the detection accuracy, It is up to customers to judge and choose.

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