Community Resources


Blower Box

The NCAR Blower Box is a compact (5.25”H x 19”W x 10”D) and inexpensive (~US$2000) flow and high voltage control unit for a differential mobility analyzer (DMA). The unit, pictured below, contains a sealed regenerative blower, two HEPA filters, and pressure, temperature, relative humidity, and mass flow meters for the DMA sheath and excess flows as well as a high voltage module for the DMA. Sensor and control voltages are interfaced with a computer via a 9-pin D connector on the front panel. Most of the parts are available directly from vendors (that is, no special machining is required) and assembly can be performed in about a day. This project is suitable for lab scientists and engineers with some experience with electrical and mechanical assemblies. A parts lists, assembly instructions and help with the assembly are available from Jim Smith (

NCAR Blower Box

Blower box built for Washington State University (top cover removed).


Bipolar Charger

The bipolar charger, shown below, places a well-characterized charge distribution onto particles using a bipolar field of ions. The NCAR design was developed in the Particle Technology Laboratory at the University of Minnesota. It requires one “Staticmaster” generally license radioactive ionizer available from NRD, LLC (model 2U500). The ionizer is housed inside a sealed stainless steel or aluminum tube, with ¼” diameter Swagelok fittings on each end of the tube. This project requires machining. A complete set of drawings and a parts list is available from Jim Smith (

Bipolar Charger




ACOM | Atmospheric Chemistry Observations & Modeling