Abstract: A micro-machined virtual impactor device to permit the separation, collection and concentration of a significant portion of environmental particulates having a diameter of less than ten microns and its method of operation. The device includes a plurality of projections, each having a virtual impact surface that defines an aperture in a stagnant zone of fluid flow. A major portion of the particulate material is concentrated into a minor portion of the fluid which is processed through the aperture, where it is collected for subsequent analysis.

Abstract: A cam assembly and method for providing a substantially constant load to a motor that drives the cam assembly. A torque compensated cam assembly (142,300) includes a plurality of tracks (140,150,152/310,312,314) that are profiled with a surface that varies radially as the cam rotates, thereby actuating cam followers, each of which rolls along a different track. A tangential force developed by the cam followers as they move over rapid radial changes in the surfaces of the tracks produces a total net torque that at times tends to aid the rotation of the cam and at times tends to impede its rotation. In the application of the torque compensated cam assembly disclosed, the cam is used in a volumetric pump (30) that accurately delivers a desired volume of fluid at a desire rate. To assist in maintaining the accuracy of these parameters, the torque compensated cam assembly presents a substantially constant load to a motor (146,304) that drives the cam.