Scanning Mobility Particles Sizer (SMPS)

Counter (CPC). Electrostatic classifier consists of impactorassembly, bipolar charger and differential mobility analyzer(DMA). First polydisperse particles enter through impactor where those larger than cut off size are removed. Then the aerosol particles enter into the Kr-85 bipolar charger, which exposes aerosol particles to bipolar ions. The sheath air and charged particles are introduced at the top of the DMA and both flow down without mixing with each other and by maintaining laminar flow.The DMA consists of two concentric metal cylinders. The inner rodmaintains negative voltage and outer cylinder is grounded thus lectric field is generated in annular space of DMA. Positivecharged aerosol particles move towards the inner rod through sheath air. The aerosol particles are sized according to their electrical mobility. Nearly monodisperse aerosols then enter intothe CPC. Here, the aerosol mixes with butanol vapor, undergoessuper saturation resulting in condensation of vapor on aerosolsurface. Consequently, the aerosol particles grow to a size that canbe detectable by light scattering.

Technical Specifications:

Impator orifice: 0.0457 cm. 0.0508 cm, 0.0701 cm, Particle Size: Long DMA: 10 -700 nm diameter, Nano DMA: 4 -150 nm. Both the DMAs can run at low and high flow rates (0 .3 and 1.5 lpm) SMPS can measure particles up to 2×108 particles cm-3.


Environmental Engineering Laboratory, WL 116
IIT Kanpur


Prof. S N Tripathi

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Figure 1