A Novel Straightforward Practice for Rotameter Calibration in Gas Flow Measurement

Rotameters for gas flow-rate measurements are calibrated and scaled by air or oxygen at standard atmospheric pressure and temperature in the fabrication plants. To utilize these rotameters for gas flow rate measurements at different conditions, they have to be recalibrated again. This is not an easy task in the labs environment and should be carried out with so much care to obtain accurate measurements at the specified operating conditions. A novel straightforward and reliable procedure for calibrating rotameters under specific lab conditions is introduced in this paper which enables researchers to practice it with usual limitations of time and budgets. The practice involves producing proper calibration curves based on the theoretical formulations. As an example, the principle of action and characteristics of an air calibrated rotameter is investigated, when it is going to measure oxygen flow rate at different pressure and temperature.  It is shown that a linear function can be derived to estimate the true flow rates of gases based on the indicated flow rate readings on the rotameter scale and the corrected flow rate mentioned in the literature.