Acceptance testing and performance testing
The American Society for Testing Material (ASTM) has defined a test procedure that most schools will want to use as part of the initial acceptance test and also incorporate into their regular performance testing. This test uses a 10-step wedge of milled aluminum (exhibit 3.14). Across the bottom of the step wedge are several wavy wires of different gauges. The x-ray detector is performing well if, when this step wedge is sent through the detector, 10 different shades of gray are clearly distinguishable and a certain number of the wires are also seen. (A very good x-ray detector will see even the smallest gauge of wire behind the thickest step of the step wedge.) This step wedge will be available through your vendor, who will likely employ the same tool for its own testing purposes.
Schools should initially run this test to accept the equipment and on a regular basis, such as once a month, for validating that the system is still performing well. Any significant decrease in the number of wavy wires that are visible may indicate that the unit needs repair.
Research Report: The Appropriate and Effective Use of Security Technologies in U.S. Schools