Differential Electrical Mobility Classifier from 4 to 600 nm

Particle-free sheath air in the column leads the aerosol flowing in at the annular gap of the column to the opposite side of the column. At the same time an electric field from the inner column outer wall to the inner center electrode moves the particles horizontally to the electrode in an electric field (capacitor), drift after a short acceleration with constant velocity and either reach the upper inner annular gap (exit to the counter) or are deposited at the electrode or are carried out of the column via the sheath volume flow and filtered off.

The change of the applied voltage at the electrode of the column (typically in the range of a few volts up to max. 10 kV) leads to different horizontal drift velocities in the column depending on the particle size and the number of charges on the particle. An "inversion algorithm" can be used to infer the particle size and concentration, as described in ISO 15900:2000. Instead of selecting individual particle sizes, the systems can display the size distribution and concentration in the set range in scan mode.

With a short classifying column (model 1000), the Palas^® DEMC is suitable for the size range 4 to 600 nm. The basic control unit is available with (DEMC 1000 X) and without (DEMC 1000) X-ray neutralizer and can be combined with appropriate counters from the Palas^® ENVI-CPC/UF-CPC system series or an electrometer such as charme^® to measure aerosol concentration.

All settings are directly accessible via the 7" touch screens, which are also used for the first graphical processing and already allow first comparisons. Measured values and sensor data are immediately and continuously recorded.

Extensions/Accessories

The DEMC system is usually used for the generation of monodisperse aerosol but can be coupled via different interfaces (USB, LAN, WLAN, RS-232/485) with further systems, e.g., of a counter (in scan mode to the U-SMPS system or for the measurement of the number concentration of selected quantities in calibration mode).