ASTM C1270:97(R2021) pdf free download – Standard Practice for Detection Sensitivity Mapping of In-Plant Walk-Through Metal Detectors.
4.2 This practice describes two methods for determining the values that make up the detection sensitivity map:
4.2.1 In the first, a test object, which is usually specified by requirements of the responsible regulatory authority, is passed through the detection zone in each of the identified test paths and the sensitivity is adjusted to determine the lowest sensitivity setting that results in consistent detection of the test object in each test path. These settings arc the critical sensitivity settings and are the value entered in the respective elements of the detection sensitivity map.
4.2.2 If a detector has a numeric readout that is representative of the actual signal from which the detector determines an alarm condition, this value may be used for describing the detection sensitivity pattern. In this case, a specified test object is passed through each test path several times and the mean value of the responses is calculated for each element (the sensitivity adjustment must be set at a level that provides less than full scale readings for the most sensitive path through the detection zone). These mean values describe the sensitivity pattern.
4.3 Test objects that are orientation sensitive must have each orthogonal orientation tested to determine the worst-case orientation.
5. Significance and Use
5.1 A complex set of variables affect metal detection and detection sensitivity. Some physical characteristics of metal objects that influence detection are material composition. shape, surface area, surface and internal electrical and magnetic properties, and finish. The orientation of a test object can greatly influence detection as can the direction and speed or changes in speed while passing through the detection zone. Nearby large metal objects and metal moving in near proximity to a metal detector also affect operation, as do temperature and humidity, and can he a cause for nuisance alarms. Additionally, most currently manufactured walk-through metal detectors have some means for programming the operation of the detector for special conditions or requirements; these variables and the effect they have on the operation of in-plant detectors must be considered if a test program is to be effective. This practice is intended to minimize the impact of these variables on the operation of in-plant detectors by systematically testing the installed detectors in the operating environment with the test object(s) specifIed by the regulatory authority requirements.
5.2 This practice may be used to determine the critical test object from a group of test objects. its critical orientation, and the critical test path through the detection zone. This information may allow the use of a single test object for setting the operational sensitivity of the detector and performing periodic performance evaluations necessary to ensure a high probability that all test objects in the group are detectible within the capabilities of the detector.