An Improved Instrument for Measuring Filter Rod Pressure Drop

A compact, portable pressure-drop instrument that incorporates modern electronic pressure-drop measuring techniques has been designed and built. It includes a built-in laminar-flow calibration standard. The new design offers virtual independence from external capillary standards (and the associated problems of maintaining capillary cleanliness), fast digital readout, potential for automatic data processing, and a simple method of flow-rate adjustment at different filter rod pressure drops. Pressure drop measured with the new instrument meets the CORESTA-recommended definition of pressure drop for filter rods. Data collected on the new instrument show that the average and percent coefficient of variation of pressure drops measured on the new instrument compare favourably with data collected by the previously used standard instrument having mainly a vacuum pump, needle valve and water column manometer.