A GAS-FLOW STANDARD APPARATUS

A gas flow standard apparatus is introduced. It is a kind of calibrati on apparatus of gas throughput and can be used to calibrate a gas flow meter and reference leak. It consists of the following main parts: a c onstant pressure flowmeter, a calibration system, a flow inlet system and a measurement and control system. Hydraulically driven bellows are used for the variable chamber of the constant pressure flowmeter. A c onstant torque servo motor drives a guide system to realize the horizo ntal motion of the piston. A precision grating ruler is used to measur e the piston displacement. The measurement and control system maintain s the pressure difference between variable chamber and reference chamb er at less than 0.01% of the reference chamber pressure. The gas flow standard apparatus can calibrate the throughput with the direct method of measurement and the comparison method of measurement. Its calibrat ion range is 1 x 10(-5)-23 PaL/s with the uncertainty at less than 2%. Copyright (C) 1996 Elsevier Science Ltd.