Patent ID: 8011258

Claim:
An apparatus comprising: a head configured to receive a pad and rotate to apply a shear force to the pad for sampling explosive residue on a surface; a feedback system coupled to the head, the feedback system configured to restrict the shear force applied by the head to be within a predetermined range, wherein the head is configured to apply pressure to the pad, and the feedback system includes a pressure sensor for sensing the pressure applied by the head to the surface; and a processor coupled to the pressure sensor, the processor configured to: determine that a pressure sensed by the pressure sensor is greater than a minimum threshold value and less than a maximum threshold value, activate a motor to rotate the head based on the determination, determine a duration of time during which the head applies pressure to the pad, compare the determined duration to a preset length of time, and deactivate the motor if the determined duration is equal to or greater than the preset length of time.