Electrical calibration method for cascade impactors

A new method for measuring collection characteristics of cascade impactors is described. The method is based on challenging the impactor with monodispersed charged particles and measuring electrical currents on all the impactor stages plus a backup filter. From the current values, collection efficiency at a certain particle diameter can be calculated simultaneously for each impactor stage. To test the method, monodispersed dioctyl sebacate particles were generated using an atomiser, evaporation/condensation generator and an electrostatic classifier. The particle collection characteristics of the six lowest stages of a Berner-type low-pressure cascade impactor were measured. Comparison measurements were made with a real-time stage efficiency measurement system for single impactor stages. The results of the two methods were in good agreement.