Detailed information on the calibration procedure for the orifice flow meter can be found in Barbosa and Pinho (2004).
Along the vertical testing section, pressure taps were fitted half a meter apart. The first pressure tap is 0.5 m away from the bend connecting the horizontal feeding section and the vertical testing section. For the pressure drop measurements along the conveying pipe, differential pressure transducers in the 0 to 490 Pa range were used. The transducers were from Series T of Modus Instruments, Inc., and had output signals of 0-1 V dc. The transducers outputs were checked towards U-type water manometer readings. A data acquisition system (DAS 1601 plus EXP 16 boards) installed on a personal computer received information from the differential pressure transducers on use (for the orifice plate pressure drop and the conveying pressure drop), as well as temperature readings of the conveying air through a type T thermocouple, Fig. 2. The accuracy of differential pressure drop measurements considering also the data acquisition process was of 9.7 Pa for the 0 - 1245 Pa pressure transducer, and of 7.9 Pa for the 0 - 490 Pa pressure transducer.