A weapon can be strapped to the wrist and carried through by swinging the wrist ahead of the body torso as entry is made. Most manufacturers recommend adjusting sensitivity levels by passing metal objects through the center of the archway for this very reason. However, performance higher and lower in the detector may be seriously compromised. The opposite of the above. This is an area or areas within the field which are markedly less sensitive to metal, generally at the top and bottom.
Some detectors have fields which vary from moment to moment, constantly shifting around.
Cumbersome elevated ramps at the base are sometimes seen in high security applications because of this problem. Transit speed Some walk through detectors will alarm only in a narrow range of the speed with which a metal object is carried through. A very slow passage, such as an elderly frail person going through, may result in no weapons detection. Conversely a very fast speed, a weapon tossed through the archway for example, may not be detected either. Sensitivity drift Most walk through detectors suffer from a constantly shifting sensitivity level, which often results from changes in ambient humidity and temperature.