Abstract: The pressure drop through and the circumference of filter rods for cigarette filters or the like are determined by a completely automated rod test station that consists of a measuring unit and a computer. The measuring unit has a transport system for rapidly moving a filter rod first into a pressure drop gauge and next into a pneumatic circumference gauge and then ejecting it. A single pressure transducer in the measuring unit detects the pressure drops across the standard, through the filter rod in the pressure drop gauge and through the annular passage between the rod and die in the circumference gauge. The analog electrical signals produced by the transducer are converted to digital signals which are input to a computer. The computer corrects the measured signals indicative of pressure drop in accordance with any error detected between the measured drop across the calibration standard and a stored internal constant representing the calibrated pressure drop for the standard during each test sequence.