Explosive residue sampling

Abstract

In one aspect, an apparatus includes a head configured to receive a pad for sampling explosive residue on a surface and a feedback system coupled to the head. The feedback system is configured to indicate when a pressure applied by the head is greater than a minimum threshold value. In another aspect, an apparatus includes a head configured to receive a pad and rotate to apply a shear force to the pad for sampling explosive residue on a surface. The apparatus includes a feedback system coupled to the head, which is configured to restrict the shear force applied by the head to be within a predetermined range. In another aspect, a method includes applying pressure to a pad to sample explosive residue on a surface, sensing the pressure applied to the pad, and providing an indication of when the pressure applied to the pad is greater than a threshold value.

1 . An apparatus comprising:
 a head configured to receive a pad that, when applied to a surface, samples explosive residue on the surface; and   a feedback system coupled to the head and configured to indicate when a pressure applied by the head to the surface is greater than a minimum threshold value and less than a maximum threshold value, the feedback system comprising:
 a pressure sensor for sensing a pressure applied by the head to the surface; and 
 an electronic processor coupled to the pressure sensor and configured to determine when a pressure sensed by the pressure sensor is greater than the minimum threshold value and less than the maximum threshold value. 
   
     
     
         2 . The apparatus of  claim 1 , further comprising a handle coupled to the head and grippable by a human operator, wherein the handle is configured to be manipulated by the operator to cause the head to apply pressure to the surface. 
     
     
         3 . The apparatus of  claim 2 , wherein the feedback system is further configured to present an indicator when the pressure sensed by the pressure sensor is greater than the minimum threshold value as the head applies pressure to the surface. 
     
     
         4 . The apparatus of  claim 2 , wherein the feedback system is further configured to restrict a shear force applied by the head to be within a predetermined range. 
     
     
         5 . The apparatus of  claim 2 , further comprising the pad.