Patent ID: 7806968

Claim:
A penetration and removal efficiency calibration unit for a volatile particle (VPR) or a calibration unit for a condensation particle counter (CPC), the calibration unit comprising: a flow meter measuring a flow rate from a differential mobility analyzer and providing an output flow; a mixer receiving the output flow from the flow meter and receiving a flow of particle free dilution gas, the mixer providing a mixer output flow, wherein a portion of the mixer output flow is provided to the VPR or CPC; a first flow controller for controlling the flow of particle free dilution gas to the mixer; a bypass inlet receiving a bypass flow, the bypass flow being the remainder of the mixer output flow that bypasses the VPR or CPC; a second flow controller receiving the bypass flow from the bypass inlet, for controlling the bypass flow; a vacuum source drawing the bypass flow into the second flow controller; and a control loop controlling the bypass flow such that the aerosol flow from the differential mobility analyzer tracks a reference value as the flow into the VPR or CPC varies.