Detectors based on semiconductors, notably hyperpure germanium, have better intrinsic energy resolution than scintillators, and are preferred where feasible for gamma-ray spectrometry.
At the same entrance, three private security guards frisked churchgoers with hand-held metal detectors, while a fourth guard used a mirror to check for explosives underneath cars.
For measuring speed or direction, a device uses multiple detectors and calculates the speed from the relative distances to particulates in the air or water.
For the city airport, the proposed equipment include a unit of final security checkpoint x-ray, a walk through metal detector, two hand-held metal detectors and a cargo security checkpoint x-ray.