PARTICLE COUNTER

Model PEM-PC 2

Salient Features

Microprocessor- based user programmable

User-friendly fully automatic operation

Direct display of particle concentration

Compact, light-weight, portable

Application

Particle Counter Model PEM-PC 2 is an advanced microprocessor-based instrument, which is user programmable to facilitate automatic measurement and direct display of the number of particles per unit volume of the sampled air.

Principle of Operation

PEM-PC 2 utilizes the well-known fact that under suitable operating conditions of super saturation, small particles have the ability to act as condensation centers for water vapour.  Further, upon condensation of water these particles grow in size leading to fog formation. The degree of fog gives a measure of particle concentration.

The particles from the atmosphere are sampled into the sampling chamber where moist blotting paper provides the saturated atmosphere. Adiabatic expansion of the air due to sudden connection of the sampling chamber to the evacuated auxiliary chamber through the quick opening valve results in super saturation and consequent fog formation in the sampling chamber.  Limited size discrimination can be achieved by controlling the partitioning volume in the auxiliary chamber.

Construction

The specifications and design of various components of the sampling system are based on Gardener's Condensation Nuclei Counter. However, PEM-PC 2 utilizes a solid-state light source, which affords longer life and lower drift. The control unit is a microprocessor-based system. The optical system is calibrated for each sample. Also for each sample, a number of readings are taken, which are processed on-line and the peak is computed. The computed data is stored in the internal non-volatile memory for subsequent retrieval. The system also provides a printer port for getting a printed record of the measurements / computations. The Total Sampling Duration, Sampling interval, minimum vacuum and minimum humidity set points are user programmable. The system also comprises an intelligent user-machine interface for setting sampling and control parameters and displaying the status of the various parameters and control devices.