A new approach to gas flow calibration

Primary gas flow standards create calculable flow rates using two different techniques. Displacement systems rely upon the accurate determination of the first order change in position of an object being displaced by gas flowing at a constant pressure. Pressure, volume, temperature and time (PVTt) systems provide a nearly constant mass flow of gas to an accumulation tank of known volume over a fixed time interval. Measurements of pressure, temperature and time are used to calculate flow rate.The Precision Gas Flow Calibrator (PGFC) described below represents a new and simplified approach to gas flow calibration. By setting the parameters which drive the exponential decay of pressure from a fixed volume a range of flow rates is generated which is linear to first order within measurement times sufficient for obtaining high precision data. Indeed, previous work has proven this method as effective as displacement based standards for an orifice flow calibration system [1].